SPERMATOGENESIS 499 



Henking finds that the primordial sperm-cells correspond to the 

 primordial ova, both forms of cells in the insect he studied contain- 

 ing the characteristic number of twenty-four chromosomes. 



The spermatogenesis of Laphria, according to Cholodkowsky, is very peculiar, 

 and strongly resembles that described by Verson in Bombyx mori. In the 

 blind end of the testicular tubes lies a colossal cell visible to the naked eye, the 

 spermatogone, from which the entire contents of the testes originate. In Bom- 

 byx this spermatogone appears in the larva state. Such colossal spermatogones 

 also occur in Lepidoptera of different families (Hyponomeuta, Vanessa, and in 

 the p'upa of Choreas graminis), in Trichoptera, and in Hemiptera (Syromastes) ; 

 and Cholodkowsky inquires whether they may not be typical of insects. Toyama 

 has observed these colossal cells not only in the testes but also in the ovaries of 

 the silkworm. He regards them as supporting cells. 



The spermatozoa are inclined to remain in bundles, and in this 

 state are expelled during copulation. These bundles are either root- 

 like, bushy, string-like, sinuous, or worm-like. 



Auerbach has observed the spermatozoa of Dyticus marginalis in their passage 

 through the convoluted seminal vesicles. All those arising from one testicular 

 tube are united in a bundle. Each has a very complex structure, bilateral but 

 unsymmetrical. The right side of the head is concave, the left convex ; the 

 whole head is longitudinally curved to right or left ; and on the posterior half of 

 the right side there is a projecting ridge bearing a hook-shaped cyanophilous 

 " anchor," at the free end of which an erythrophilous spherule appears. The 

 most remarkable fact is that the spermatozoa unite in pairs in a perfectly definite 

 way, opposed and crossed in a manner somewhat suggestive of a pair of scissors, 

 with the right sides of the heads in contact. During this conjugation, or " deju- 

 gation" as Auerbach calls it, the anchors change their shape, and the little 

 spherules are lost. Hundreds of these double spermatozoa are found together in 

 little balls. The conjugation is a temporary one, but it may permit a molecular 

 exchange of substance, perhaps with the result of mixing the hereditary qualities 

 and limiting variability. (Journ. Roy. Micr. Soc., 1893, p. 622.) 



In many insects which lack a true penis, the bundle of spermatozoa 

 are united in the ejaculatory duct, forming packets which are en- 

 veloped by the secretion of the accessory glands which stiffens into 

 a hard case. These packets are called spermatophores. They are 

 either introduced into the vagina of the female or simply remain out- 

 side. Graber has repeatedly observed that the male crickets, in the 

 absence of the female, let their spermatophores fall to the earth ; 

 whether it is afterwards made available is not known, because 

 hitherto no case is reported that females seeking impregnation 

 search, as in the case of the Isopod crustacean, Porcellio, for the 

 spermatophores. 



In the Gryllidse and Locustidse the spermatophore lies in a cup-like cavity 

 under the penis. This is called the "spermatophore cup" (Chadima, 1871), 

 into which the ejaculatory duct of the testis opens. 



