6 



THE AMERICAN BEE JOURNAL. 



[July, 



tions of the development of the cahbage-buttei'- 

 fly : The orgaus which produced by the formative 

 power from the linid of the egg are, a nervous 

 system, a muscuhir system, an air-vessel sys- 

 tem, and an alimentary system, together with 

 the salivary and biliary vessels belonging to the 

 latter — also, a pair of excretory organs, (namely, 

 the sperming vessels, ) a dorsal vessel, and lastly 

 the germs of undeveloijed reproductive organs, 

 with a. perfectly, distincdy visible distinction of the 

 two sexes. 



On the fifth plate of the under-mentioned 

 work,* he gives an exceedingly instructive and 

 true view of the germs of the reproductive organs 

 of both sexes, as these gradually enlarge from 

 the first formation of the cabbage-caterpillar in 

 the egg up to its full growth and approach to 

 transformation. In figure one, he shows the 

 two reniform corpuscles divided by three con- 

 structions into four sections, lying one behind 

 the other, (the future testes, ) the two filaments 

 issuing from them laterally (the future ducts 

 eft'erent), from a male caterpillar which had 

 crept out of the egg a few hours before ; whilst 

 in figure two, of tlie same plate, we may recog- 

 nize the two bud-like corpuscles with four later- 

 ally approximated sausage-like divisions, and 

 two filaments springing from behind, as the fu- 

 ture ovaries and oviducts of a female caterpillar 

 of similar age. I will not, however, conceal 

 that Hermann Meyer did not succeed in finding 

 the sexual parts in caterpillars which were only 

 a few days old. On the other hand, Weisemann, 

 in his remarkable work on the embryology of 

 insects, completely afiirms the correctness of the 

 observations first made by Harold in butterflies, 

 of the occurrence even in the embryo of the 

 germs of the sexual glands, with distinctly visi- 

 ble distinction of the sex, inasmuch as he could 

 likewise distinguish the rudiments of the sexual 

 glands in the embryos of files in the egg, al- 

 though the difference between the germs of the 

 male and female sexual glands is much less 

 striking. In the investigation of a Tipulidte 

 larvae, however, Weissmann obtained other re- 

 sults, which I must not pass over. When he 

 souglit the genital glands in the embryos of 

 Corethra plumicornis, he certainly satisfied him- 

 self that in this insect also, as in the larvas of 

 the true flies, the sexual glands are already 

 traced out in the embryo ; but he found that in 

 the larvpe of Corethra ^\\?,t escaped from the Qgg, 

 the distinction is as yet by no means clear : and 

 this distinction does not make its appearance in 

 a marked manner until after the fourth change 

 of skin. From Mecznikow's very accurate em- 

 bryological investigation in insects it appears 

 also, that although the tracing out of the sexual 

 glands takes place very early in all embryos of 

 insects, their further development does not ad- 

 vance at an equal rate in all such embryos ; so 

 that it is only in certain insects that the differ- 

 ence of the sexual organs occurs very early, and 

 indeed already in the embryos ; whilst in other 

 insects, on the contrary, it is postponed, and 

 takes place only in the excluded larvaj. In the 

 very young larv£e of a Simulia iwat escaped from 



the egg, Mecznikow observed a small round 

 genital rudiment, and concluded froiii this that 

 the rudiments of the sexual orgaus are formed 

 in the larvse within the egg. 



The same author recognizes, even at the first 

 formation of the embryo in viviparous ai^hides, 

 the rudiments of the sexual apparatus, as the 

 so-called genital hill. During the further devel- 

 opment of the embryo, and indeed very early, 

 this genital rudiment becomes differentiated into 

 ovarian tubes, in which so-called pseudova are 

 likewise very soon developed ; so that even dur- 

 ing the embryonal life of the aphis-embryo, the 

 development of the new generation commences, 

 and goes so far that in the embryo ready to be 

 born two germ chambers occur in each ovarian 

 tube, of which the lowest already encloses an 

 embryo in the first stage of its development. 



In Aspidiotus Nervi, on the contrary, Meczni- 

 kow could not find any genital hill so early pro- 

 duced and diffci'entiated into ovarian tubes, such 

 as he succeeded in distinguishing in aphides. 

 From these known circumstances in the first de- 

 velopment of the reproductive organs of insects, 

 it appears that differences occur in it, and that 

 in a certain series of insects the differentiation 

 of the sexual apparatus occurs in the embryos 

 while still enclosed in the egg-shell, whilst in 

 other insects this differentiation only takes 

 place after the exclusion of the larvse. Lan- 

 dois' theory can certainly find no application 

 to the insects belonging to the first series — 

 namely, the Lepidoptera and Flies, (Muscidce,) ; 

 and in the second series, in which the Corethra, 

 Simula, and Aspidiotus are to be placed, it may 

 be possible that the still rudimentary and indif- 

 ferent sexual glands of the larvse are farther de- 

 veloped, in accordance with the male or female 

 type, under the influence of the incepted nour- 

 ishment. 



When, and in what manner, in the larvae of 

 the bees, the first rudiments and the different 

 differentiation of the sexual glands appears, we 

 have no direct investigation to show. I earnestly 

 recommend such investigation to entomologists 

 for the solution of the question before us. 

 Leuckart, howevei', has already given an indica- 

 tion in this direction*, when he says, " On the 

 sixth day I find in the female larvas the first 

 trace of internal genitalia." 



With regard to the above-mentioned discovery 

 of Mecznikow's of the development in the em- 

 bryo of viviparous aphides of ovaries, in the 

 germ-chambers of which the formation of a 

 new generation was already commenced, M. 

 Landois has informed me by letter under date 

 of the 5th of May, that he has succeeded by the 

 gradual application of artificial cold and during 

 the withering of the food-plants, to cause the 

 disappearance of the viviparous aphides (the 

 so-called nurses,) and the appearance in their 

 stead of the sexual generation consisting of 

 males and ovipositing females. I cannot doubt 

 the result which Landois has obtained from his 

 experiment ; but I will take the liberty of put- 

 ting the question : " How, in this case, does the 

 production of the two sexes simultaneously with 



*Entwickelungeschiclite der Schmetterliuge, Basel und 

 Marburg, 18iO, p 1. 



*Bieaenzeitung 186"i, p. 210. 



