48 STUDIES IN SPERMATOGENESIS. 



slightly earlier stage before synapsis, there were found two pairs of 

 chromosomes (fig. 271, x lt xz, and m l , m 2 ) which were stained with 

 safranin in contrast with the violet spireme. These two pairs I 

 interpret as being (i) the homologues of the pair of w-chromosomes, 

 which remain condensed during the growth stage of the spermato- 

 cytes, and (2) a pair of heterochromosomes corresponding to the odd 

 chromosome of the male. Various combinations of these heterochro- 

 mosomes are shown in figures 272-277. Figures 278 and 279 were 

 taken from mercuro-nitric material stained with iron-hsematoxylin. 

 In section 278 the " bouquet" was cut through, showing the bivalent 

 corresponding to the larger pair in figure 271, and in figure 279 this 

 element is seen behind the paler loops. The history of these two pairs 

 of heterochromosomes, which have not, so far as I know, been found 

 before in oocytes, should be followed up in older ovaries, and related 

 species should be examined for similar phenomena. 



LEPIDOPTERA. 

 Cacoecia and Euvanessa. 



I had no intention of making an extended study of the spermato- 

 genesis of the Lepidoptera, but was interested to see if anything cor- 

 responding to the heterochromosomes of other orders could be found. 

 The material studied was the testes of the larvae of Cacceda cerasivor- 

 ana and Euvanessa antiopa. The number of chromosomes is large, but 

 the equatorial plates are diagrammatically clear. In. both species 30 

 chromosomes are found in both first and second spermatocytes. In 

 both, one chromosome is larger (figs. 290 and 293, x). In the growth 

 stage (figs. 283, 284) there is a two-lobed body (or sometimes two sep- 

 arate spherical bodies) which seems to correspond in size to the larger 

 pair of chromosomes in the first spermatocyte. In iron-haematoxylin 

 preparations this pair is often obscured by parts of the spireme which 

 are tangled around it. In safranin-gentian preparations it stains, not 

 like a plasmosome, but red like the heterochromosomes, while the spi- 

 reme is violet. The staining reaction at least suggests that this equal 

 pair of chromosomes, which may be traced through the synizesis stage 

 (fig. 280), synapsis stage (figs. 281, 282), growth stages (figs. 283, 284), 

 and prophases (figs. 285-287), into the first spermatocyte spindle (figs. 

 288, 290), and on to the second spermatocyte (figs. 289, 291, 292), is 

 an equal pair of heterochromosomes comparable to the equal pair of 

 1 ' idiochromosomes ' ' found by Wilson in Nezara ('05). As the various 

 stages are practically the same in Euvanessa antiopa, but somewhat 

 clearer in Cacceda, only one figure is given for Euvanessa the equa- 

 torial plate of the first spermatocyte (fig. 293). 



