ON THE DEVELOPMENT OF PARASITIC COPEPODS. 47 



(Fig. 1 6). From these spheres radiate strands of protoplasm 

 simulating astral rays, but not so dense. The spindle is formed 

 parallel to the flat surfaces of the egg and then begins to rotate 

 to a perpendicular position, at the same time shortening (Fig. 17). 

 In this state it remains until fertilization, and further than this I 

 have not followed it. The behavior of the linin sheath of the 

 chromosome is very peculiar, and it seems to be more conspic- 

 uous than in any other instance I know of. The spindle, in 

 general appearance,, resembles the first cleavage spindle of 

 Cyclops (Hacker). 



V. SPERMATOGENESIS. 

 Lcemargus mnricatns. (Preliminary Notice^ 



The spermatogonia are small cells with comparatively large 

 spherical nuclei, and are arranged in single linear series. The 

 nucleus contains chromatin granules in a peripherical linin retic- 

 ulum. When preparing for mitosis these granules become 

 arranged into looped rows, but I have not ascertained whether 

 these rows form a continuous spireme or not. There is a single 

 large nucleolus. In the last spermatogonic divisions there are 16 

 chromosomes (twice the number of the spermatocytic divisions). 

 The preliminary spermatocytes are half the size of the spermato- 

 gonia when first formed, and are arranged in single linear series. 

 Whether there is a single chain or cord of cells in the testes as 

 in the ovaries, I cannot tell, owing to the many convolutions, 

 but think there are at least several such chains or cords. The 

 regular growth of these causes the testis to be divided into zones. 

 During the growth period the cells grow to the size of the sper- 

 matogonia and cannot be distinguished from them save by their 

 position in the testis (growth zone). When preparing for division 

 the cells lose their linear arrangement ; the chromatin forms 

 eight double rods which lie close together (synapsis stage). 

 Each double rod becomes ring shaped and the rings contract 

 until only a small lumen is left. An additional pair of constric- 

 tions converts the ring into a tetrad. The division forms two 

 secondary spermatocytes, each with eight diads, and another 

 division immediately following forms four spermatids, each with 

 eight chromosomes. The spermatids are grouped in fours. In 



