Fig. 311.—Silver Surf-fish (viviparous), Hypocritichthys analis (Agassiz). Monterey.
The details of structure vary greatly among the different species, for which reason almost every species has been properly made the type of a distinct genus. The two species found in Japan are Ditrema temmincki and Neoditrema ransonneti. In the latter species the female is always toothless. Close to Ditrema is the blue surf-fish of California, Embiotoca jacksoni, the first discovered and perhaps the commonest species. Tæniotoca lateralis is remarkable for its bright coloration, greenish, with orange stripes. Hypsurus caryi, still brighter in color, orange, green and black, has the abdominal region very long. Phanerodon furcatus and P. atripes are dull silvery in color, as in Damalichthys argyrosomus, the white surf-fish, which ranges northward to Vancouver Island, and is remarkable for the extraordinary size of its lower pharyngeals. Holconotus rhodoterus is a large, rosy species, and Amphistichus argenteus a large species with dull yellowish cross-bands. Rhachochilus toxotes is the largest species in the family and the one most valued as food. It is notable for its thick, drooping, ragged lips. Hyperprosopon arcuatus, the wall-eye surf-fish, is brilliantly silvery, with very large eyes. H. agassizi closely resembles it, as does also the dwarf species, Hypocritichthys analis, to which the Japanese Neoditrema ransonneti is very nearly related. The other species are all small. Abeona minima and A. aurora feed on seaweed. Brachyistius frenatus is the smallest of all, orange-red in color, while its relative, Zalembius rosaceus, is handsomest of all, rose-red with a black lateral spot. Cymatogaster aggregatus, the surf-shiner, is a little fish, excessively common along the California coast, and from its abundance it has been selected by Dr. Eigenmann as the basis of his studies of these fishes. In this species the male shows golden and black markings, which are wanting in the silvery female, and the anterior rays of the anal are thickened or otherwise modified.
No fossil embiotocoids are recorded.
The viviparity of the Embiotocidæ was first made known by Dr. A. C. Jackson in 1863 in a letter to Professor Agassiz. From this letter we make the following extracts:
"A few days, perhaps a week, after the four trials, and on the 7th of June, I rose early in the morning for the purpose of taking a mess of fish for breakfast, pulled to the usual place, baited with crabs, and commenced fishing, the wind blowing too strong for profitable angling; nevertheless on the first and second casts I fastened the two fishes, male and female, that I write about, and such were their liveliness and strength that they endangered my slight trout rod. I, however, succeeded in bagging both, though in half an hour's subsequent work I got not even a nibble from either this or any other species of fish. I determined to change the bait, to put upon my hook a portion of the fish already caught, and cut for that purpose into the larger of the two fish caught. I intended to take a piece from the thin part of the belly, when what was my surprise to see coming from the opening thus made a small live fish. This I at first supposed to be prey which this fish had swallowed, but on further opening the fish I was vastly astonished to find next to the back of the fish and slightly attached to it a long very light violet bag, so clear and so transparent that I could already distinguish through it the shape, color, and formation of a multitude of small fish (all facsimiles of each other), with which it was well filled. I took it on board (we were occupying a small vessel which we had purchased for surveying purposes). When I opened the bag, I took therefrom eighteen more of the young fish, precisely like in size, shape, and color the first I had accidentally extracted. The mother was very large round her center and of a very dark-brown color, approaching about the back and on the fins a black color, and a remarkably vigorous fish. The young which I took from her were in shape, save as to rotundity, perfect miniatures of the mother, formed like her, and of the same general proportions, except that the old one was (probably owing to her pregnancy) much broader and wider between the top of the dorsal and the ventral fins in proportion to her length than the young were. As to color, they were in all respects like the mother, though the shades were many degrees lighter. Indeed, they were in all respects like their mother and like each other, the same peculiar mouth, the same position and shape of the fins, and the same eyes and gills, and there cannot remain in the mind of any one who sees the fish in the same state that I did a single doubt that these young were the offspring of the fish from whose body I took them, and that this species of fish gives birth to her young alive and perfectly formed, and adapted to seeking its own livelihood in the water. The number of young in the bag was nineteen (I fear I misstated the number in my former letter), and every one as brisk and lively and as much at home in a bucket of salt water as if they had been for months accustomed to the water. The male fish that was caught was not quite as large as the female, either in length or circumference, and altogether a more slim fish. I think we may reasonably expect to receive the specimens by the first of December. But I can hardly hope to get satisfactory specimens of the fish as I found it, with young well grown, before the return of the same season, viz., June. By that time I trust the facts will be fully decided, and the results, as important as they may be, fully appreciated."
Dr. Jackson's specimens came from Sausalito Bay, near San Francisco. Soon after the publication of this letter a similar discovery was made independently by Dr. William P. Gibbons, of Alameda. Still other specimens were made known in 1854 by Dr. Charles Girard, these having been collected in connection with the United States Pacific Railroad Surveys. The species first examined by Dr. Jackson was named by Agassiz Embiotoca jacksoni.
In Professor Agassiz's comments on Dr. Jackson's discovery he makes the following observations (Amer. Jour. Science and Arts, 1854):
"The female genital apparatus in the state of pregnancy consists of a large bag the appearance of which in the living animal has been described by Mr. Jackson. Upon the surface of it large vascular ramifications are seen, and it is subdivided internally into a number of distinct pouches, opening by wide slits into the lower part of the sac. This sac seems to be nothing but the widened lower end of the ovary, and the pouches within it to be formed by the folds of the ovary itself. In each of these pouches a young is wrapped up as in a sheet, and all are packed in the most economical manner as far as saving space is concerned, some having their head turned forwards and others backwards. This is, therefore, a normal ovarian gestation. The external genital opening is situated behind the anus, upon the summit and in the center of a conical protuberance formed by a powerful sphincter, kept in its place by two strong transverse muscles attached to the abdominal walls. The number of young contained in this sac seems to vary. Mr. Jackson counted nineteen; I have seen only eight or nine in the specimens sent by Mr. Cary, but since these were open when received it is possible that some had been taken out. However, their size is most remarkable in proportion to the mother. In a specimen of Emb. jacksoni 10½ inches long and 4½ high the young were nearly 3 inches long and 1 inch high; and in an Emb. caryi 8 inches long and 3¼ high the young were 2¾ inches long and ⅞ of an inch high. Judging from their size, I suspected for some time that the young could move in and out of this sac like young opossums, but on carefully examining the position of the young in the pouches, and also the contracted condition of the sphincter at the external orifice of the sexual organs, I remained satisfied that this could not be the case, and that the young which Mr. Jackson found so lively after putting them in a bucket of salt water had then for the first time come into free contact with the element in which they were soon to live; but at the same time it can hardly be doubted that the water penetrates into the marsupial sac, since these young have fully developed gills. The size of the young compared with that of the mother is very remarkable, being full one-third its length in the one, and nearly so in the other species. Indeed these young Embiotocæ, not yet hatched, are three or four times larger than the young of a Pomotis (of the same size) a full year old. In this respect these fishes differ from all the other viviparous species known to us. There is another feature about them of considerable interest, that while the two adults differ markedly in coloration, the young have the same dress, light yellowish olive with deeper and brighter transverse bands, something like the young trout and salmon in their parr dress."
