NOTE VI., CHAPTER I., p. [42]. ATTACHMENT OF THE YOUNG CRAYFISH TO THE MOTHER.
I observe that I had overlooked a passage in the Report on the award of the Prix Montyon for 1872, Comptes Rendus, LXXV. p. 1341, in which M. Chantran is stated to have ascertained that the young crayfishes fix themselves “en saisissant avec un de leurs pinces le filament qui suspend l’œuf à une fausse patte de la mère.”
In the paper already cited from the Comptes Rendus for 1870, M. Chantran states that the young remain attached to the mother during ten days after hatching, that is to say, up to the first moult. Detached before this period, they die; but after the first moult, they sometimes leave the {352} mother and return to her again, up to twenty-eight days, when they become independent.
In a note appended to M. Chantran’s paper, M. Robin states, that “the young are suspended to the abdomen of the mother by the intermediation of a chitinous hyaline filament, which extends from a point of the internal surface of the shell of the egg as far as the four most internal filaments of each of the lobes of the median membranous plate of the caudal appendage. The filaments exist when the embryos have not yet attained three-fourths of their development.” Is this a larval coat? Rathke does not mention it and I have seen nothing of it in those recently hatched young which I have had the opportunity of examining.
NOTE VII., CHAPTER II., p. [64]. THE “SALIVARY” GLANDS AND THE SO-CALLED “LIVER” OF THE CRAYFISH.
Braun (Arbeiten aus dem Zoologisch-Zootomischen Institut in Würzburg, Bd. II. and III.) has described “salivary” glands in the walls of the œsophagus, in the metastoma, and in the first pair of maxillæ of the crayfish.
Hoppe-Seyler (Pflügers Archiv, Bd. XIV. 1877) finds that the yellow fluid ordinarily found in the stomachs of crayfishes always contains peptone. It dissolves fibrin readily, without swelling it up, at ordinary temperatures; more quickly at 40° Centigrade. The action is delayed by even a trace of hydrochloric acid, and is stopped by the addition of a few drops of water containing 0.2 per cent. of that acid. By adding alcohol to the yellow fluid, a precipitate is obtained, which is soluble in water and in glycerine. The aqueous solution of the precipitate has a strong digestive action on fibrin, which is arrested by acidulation with hydrochloric acid. These reactions show that the fluid is very similar to, if not identical with, the pancreatic fluid of vertebrates.
The secretion of the “liver” taken directly from that gland, has a more strongly acid reaction than the fluid in the stomach, but has similar digestive properties. So has an aqueous extract of the gland, and a watery solution of the alcoholic precipitate. The aqueous extract also possesses a strong diastatic action on starch, and breaks up olive oil. There is no more glycogen in the “liver” than is to be found in other organs, and no constituents of true bile are to be met with.
NOTE VIII., CHAPTER II., p. [81]. ANAL RESPIRATION IN CRAYFISH.
Lereboullet (“Note sur une respiration anale observée chez plusieurs Crustacés;” Mémoires de la Société d’Histoire Naturelle de Strasbourg, IV. 1850) has drawn attention to what he terms “anal respiration” in young crayfish, in which he observed water to be alternately taken into and expelled from the rectum fifteen to seventeen times in a minute. I have never been able to observe anything of this kind in the uninjured adult animal, but if the thoracic ganglia are destroyed, a regular rhythmical dilatation and closing of the anal end of the rectum at once sets in, and goes on as long as the hindermost ganglia of the abdomen retain their integrity. I am much disposed to imagine that the rhythmical movement is inhibited, when the uninjured crayfish is held in such a position that the vent can be examined.