Tower points out that several of the varieties (or species, as he prefers to call them) were obviously recessive to decemlineata. This is most clearly demonstrated in the case of the form called pallida, which is a pale depauperated-looking creature, with the orange of the thorax almost white and the eyes devoid of pigment.[9] This form behaved as an ordinary Mendelian recessive, breeding true whenever it appeared in the cultures, or when individuals found wild were studied in captivity. A black form which Tower names melanicum was similarly shown to be a Mendelian recessive. Wild specimens of this variety of opposite sexes were not found simultaneously in nature, and there was thus no opportunity of breeding them together, but the hereditary behaviour was seen in the F2 generation from a melanicum found coupled with decemlineata. Experiments also occurred giving indication that a variety with the stripes anastomosing in pairs (tortuosa), was another recessive, and that a variety—called "rubri-vittata"—gave an intermediate F1 with subsequent segregation. All these are forms of decemlineata Stål.
Similar observations were made regarding forms recessive to multitaeniata Stål. Of these two were thrown by multitaeniata itself, namely a form named by Stål melanothorax, and regarded by him as a species, and one which Tower names rubicunda n. sp. The facts proving the recessive behaviour of their several forms will be found in the following places in Tower's book:
pallida, pp. 273-278.
melanicum, p. 279.
tortuosa, p. 280.
rubrivittata, pp. 280-281.
melanothorax and rubicunda, pp. 283-285.
Following this evidence of recessive nature of the six forms enumerated, Tower describes experiments showing, as he believes, that some of them may be caused to appear by applying special treatment to the parents during the "growth and fertilisation" (p. 287) of the eggs. The most striking example is that in which 4 males and 4 females of decemlineata were kept very hot (average 35° C.) and dry, and at low atmospheric pressure (19-21 inches). The eggs laid were restored to natural conditions. These gave 506 larvae, from which emerged 14 normal, 82 pallida and 2 "immaculothorax," viz., without pigment on the pronotum. The account of the rest of the experiment is somewhat involved, but I understand that the pallida, of which two only survived, behaved as normal recessives when bred to the type: also that the parents, after having laid the eggs whose history has been given, were restored to normal conditions and laid 319 eggs which gave 61 normals.
In another case normal parents laid 409 eggs in the hot and dry conditions, and on restoration to normal conditions, the same parents laid 840 eggs. Then 409 eggs gave 64 adults as follows:
| Males | Females | |||
| decemlineata | 12 | 8 | ||
| pallida | 10 | 13 | ||
| immaculothorax | 2 | 3 | ||
| albida | 9 | 7 | ||
| —— | —— | |||
| 33 | 31 |
The 840 eggs laid in normal conditions gave 123 normal decemlineata.
Similar experiments were made with multitaeniata and gave comparable results, the two recessives (melanothorax, rubicunda) being produced in large numbers when the parents were subjected to heat, but in this case the atmosphere was kept saturated with moisture, instead of dry, as in the previous instance. The same parents transferred to normal conditions gave normals only.
Lastly the form undecimlineata was exposed "to an extreme stimulus of high temperature, 10° C. above the average," and a dry atmosphere, with the result that from 190 eggs there emerged 11 beetles, all of the form angustovittata Jacoby, which subsequently bred true to that type (see p. 295).
In the results of these experiments, as described, there is one feature which I regard as quite unaccountable. Tower makes no comment upon it. Indeed, from the general tenour of the paper, I infer, not only that he does not perceive that he is recounting anything contrary to usual experience, but rather that he regards the result as conforming to expectations previously formed. The point in question is the genetic behaviour of the dominant normals produced under the abnormal conditions. These normals were the result of the breeding of parents declared to be at the same time giving off many recessive gametes. Some of these normals must be expected therefore to be heterozygous unless some selective fertilisation occurs. Nevertheless in every case they and their offspring are reported to have continually bred true. I allude especially to the tables given on pp. 288, 289, 292, and 293. Tower does not mention any misgiving about this result, and I think he regards himself as recounting phenomena in general harmony with the ideas of mutation expressed by De Vries. This they may be; but to anyone familiar with analytical breeding the course of these experiments must seem so surprising as to call for most careful, independent confirmation.