14 



Ing their mature form the nncleus has heoome less densely 

 stained and settles down upon the capsule like a cap. (Pigs. 

 62 to 59). It becomes thin In the center so that Its final 

 shape Is that of a cup with a rounded, thin hottom and a 

 thickened rim. This thickened border fits upon the mltoohron- 

 drlal ring so that In the mature sperm It is not possible to 

 distinguish It from that ring. 



Protoplasmic rays or pseudopodla develop out from the 

 rlm of the cup. I have been unable to determine whether they 

 arise from the mitochondrial substance or from the' nucleus. 



8. T he Sperm . 



We may now consider the structure of the mature sperm. 

 Figure 61 Is a drawing of a sperm taken from the seminal recep- 

 tacle of the female and killed in the vapor of osmlc acid then 

 stained with gold chloride after treatment with formic acid. 

 We observe the nuclear cup, n.c. from which the pseudopodla, 

 ps. arise. Inside the cup Is the spherical capsule, c. within 

 which there is the capsular oavlty, c.c; and the inner tubule, 

 l.t. with its cavity divided Into the inner tubular cavity, 

 l.t.c. ; and the outer tubular cavity, o.o. Running through 

 the Inner tubular cavity and through the wall of the inner end 

 of the tubule to the bottom of the capsule we see the central 

 body, c.b. Figure 62 was drawn from a live sperm in A% ENO3, 

 and Pigs. 63 to 65 are from sperms mounted in the serum of 

 the crab' s blood. Movements of the blood have bent the pseudo- 

 podla of these sperms. Otherwise they have more nearly the 

 natural shape and proportions than those shown in Pigs. 61 and 



