1910.] NATURAL SCIENCES OF PHILADELPHIA. 297 



ipheral end of the testis around a large cell which he considers a follicle 

 cell, in opposition to Verson's (1894) idea that it is a large sperma- 

 togonium, which by mitotic division gives rise to all the spermatogonia. 

 La Valette St. George (1897), also working on Bombyx, failed to confirm 

 Verson. Toyama finds twenty-six to twenty-eight chromosomes in the 

 spermatogonia. These split longitudinally before the formation of the 

 spindle, so that they appear in the prophase of the first spermatocyte 

 as ring-shaped bodies which are each made up of four chromosomes. 

 According to Toyama the first division of these chromosomes is trans- 

 verse ; the second is not a true division but a separation of whole chro- 

 mosomes, fourteen passing into each cell. During the spindle stage a 

 persistent nucleolus is found which shows no change in the resting stage 

 of the first spermatocytes and is seen to consist of small chromatin 

 granules imbedded in a less dense matrix. This nucleolus is later pushed 

 into the cytoplasm. Meves (1897) working on six species of Lepidop- 

 tera, confined himself largely to cytoplasmic structures. He assigns 

 a different origin to the Nebenkern from that of Butschli and Platner 

 and makes the interesting observation, for the first time, that an axial 

 filament grows out of the centrosome of the resting spermatocyte. 

 Henneguy (1897) confirms this observation of Meves for Bombijx mori 

 and Hyponomenta cognatella. 



Of the more recent contributions, Munson's (1906) on Papilio rutvlus 

 is chiefly devoted to cytoplasmic structures and is hard to bring into 

 relation with the observations of modern workers, since it shows no 

 contraction stage of the chromatin and no synapsis, " unless a temporary 

 conjugation may be considered to take place when the twenty-eight 

 chromosomes are arranged in a line of seven, four deep." These 

 "tetrads" break up into fourteen dyads. The first maturation division 

 is equational, the second, like that described by Toyama, is not a true 

 division, but a sorting of chromosomes, fourteen going to one pole, four- 

 teen to the other. In the work of Stevens and Dederer special atten- 

 tion is given to the chromatic elements. Stevens (1906) figures and 

 briefly describes the spermatogenesis of Cacoecia and Euvanessa. In 

 both species there are thirty chromosomes in the first and second 

 spermatocytes and in both there is one large chromosome, which corre- 

 sponds to the two-lobed body in the growth stage; this body stains 

 differentially in gentian-violet and can be traced through synizesis, 

 synapsis, growth stages, and both first and second maturation divisions, 

 and is interpreted as an equal pair of idiochromosomes comparable to 

 those found by Wilson (1905, b) in Nezara. Dederer (1907) studied the 

 spermatogenesis of P. cynthia. Of the thirteen chromosomes (reduced 



