L. DONCASTBR 193 



Spermatogenesis. The testis is divided into about three compart- 

 ments, and at one side of each of these is a large Verson cell round 

 which the spermatogonia are packed, not as yet visibly arranged in 

 follicles. Here and there groups of spermatogonia may be found 

 in division, indicating that the grouping which later shows itself by 

 the arrangement in follicles already exists. The equatorial plates 

 of the spermatogonia are so crowded that I have found no case in 

 which accurate observation of the chromosomes is possible ; the best 

 figures merely indicate that the number is about 30. A little distance 

 away from the Verson cell, beyond the zone in which mitoses are found, 

 the early spermatocytes, now clearly grouped in follicles, are seen to 

 pass through phases comparable with those described in the young 

 oocytes. Since the arrangement of the follicles is irregular, and all 

 the cells in any follicle are nearly at the same stage, it is less easy 

 to place the stages in their right order, but by comparison with the 

 oocyte stages no doubt remains that the cells pass through a similar 

 synizesis followed by a stage with long intertwined chromosomes, and 

 then appear to contract into chromatic bodies round the nuclear mem- 

 brane, connected by a fine reticulum. I have not found anything 

 exactly comparable with the short double chromosomes found in the 

 oocytes, but the last stage mentioned, which persists until the sper- 

 matocyte is ready for division, doubtless represents it. The chromatin 

 nucleolus is also similar to that of the oocyte at the corresponding stage. 

 During these processes the cells enlarge considerably, and the follicles 

 grow still more rapidly, so that each comes to contain a considerable 

 cavity. In some testes, perhaps occasionally in all, certain follicles and 

 their contained cells fail to grow, and when these cells come to divide 

 in the spermatocyte divisions, the mitotic figures are irregular and very 

 similar to the abnormal divisions which I have described in Abraxas. 

 They are much less frequent in Pieris, and I have not followed the 

 subsequent fate of the spermatids in this form. 



The normal spermatocyte divisions are remarkably regular and 

 clear, and show with great regularity 15 chromosomes when the 

 equatorial plate is seen in face (Figs. 6, 7). Three of these are 

 always smaller than the rest, and usually one somewhat less small 

 is distinguishable ; these four correspond with the eight smaller chro- 

 mosomes observed in the oogonial equatorial plates. Side views of 

 the metaphase and early anaphase stages of the first division show 

 that the chromosomes divide in the heterotype manner, the separating 

 halves being connected for a time by two strands. 



