52 THE CLASS OF INSECTS. 



"germ-ball" essentially agreeing with the ovary, and the asex- 

 ual larvae begin life as egg-like bodies developed from this 

 germ-ball, just as eggs are developed in the little tubes of 

 which the ovary is an aggregation. Hence these worms bud 

 out from the germ-stock, just as we have seen in the case of 

 the Aphides. Leuckart and Wagner farther agree, that " the 

 so-called chorion never being formed in either of them, the 

 vitellus [yelk] remains without that envelope which has so re- 

 markable and peculiar a development in the true egg of in- 

 sects." .... "The processes of embryo-formation agree in 

 all essential points with the ordinary phenomena of devel- 

 opment in a fecundated egg, exactly as has been proved (by 

 Huxley) to be the case in the Aphides" .... "The only 

 difference consists in the germ-chambers of the Cecidomyide 

 larvae separating from the germ-stock, and moving about freely 

 in the cavity of the body, whilst in the Aphides they remain 

 permanently attached, and constitute an apparatus which, in 

 its form and arrangement, reproduces the conditions of the 

 female organs." 



Thus we can neither pronounce these so-called larvce to be 

 larvae so long as they produce young, neither are they actual 

 males or females ; they are what Leuckart calls asexual forms, 

 which produce false-eggs (pseudova of Huxley, as restricted 

 by Leuckart). This is paralleled by the asexual Aphides, and 

 among Hj^menoptera by the worker Ants, and worker, or, as 

 they were formerly called, neuter Bees, the latter of which have 

 been known to produce young without the interposition of the 

 male ; thus the two sexes, at least the females, are dimorphic, 

 i. e. for certain exigencies of life they are specialized into two 

 distinct forms, one (as in the asexual Aphis) to produce an un- 

 limited number of young during the summer ; the other and 

 sexual, normal form to produce in the autumn a comparatively 

 limited number of eggs. 



Dimorphism is intimately connected with agamic reproduc- 

 tion. Thus the asexual Aphis, and the perfect female, may be 

 called dimorphic forms. Or the perfect female may assume 

 two forms, so much so as to be mistaken for two distinct spe- 

 cies. Thus Cynips quercus-spongifica occurs in male and female 

 broods in the spring, while the fall brood of females were 



