SPERMATOGENESIS OF AMERICAN CRAYFISH 619 



ball would correspond to the rest of the spermatozoon (figs. 67- 

 68, R). Andrews ('04), in describing the spermatozoon of 

 Cambarus affinis states: 



The most conspicuous part of the sperm is the well known vesicle 

 that makes up about one-half the bulk of the sperm. This structure 

 gives the sperm as seen from above or from below, the appearance of 

 being chiefly two concentric eUiptical rings. Side views, however, 

 . . . . make the character and relationships of the vesicle intelli- 

 gible. The vesicle is an elliptical bowl, inverted and with thick walls 

 that are invaginated at the mouth and somewhat turned back into the 

 cavity. The walls are highly refractive and so is the material filling 

 the bowl This bowl is set in the body of the sperm some- 

 what as a very small inverted cup might be held in the hollow of one's 

 closed hand. The body of the sperm is clear and more watery-looking 



than the bowl In the bottom of the sperm are some 



droplets. 



5. Uncoiling of the mature spermatozoon 



The opening of the spermatozoon was studied by teasing out 

 mature sperm from the vas deferens in hanging drops of Ringer's 

 solution, in weak solutions of various salts such as KCl, NaCl 

 and KNO3, or in water, and studying these under the 2 mm. oil 

 immersion objective. The best resiilts were obtained in Ringer's 

 solution. When the spermatozoon comes in contact with this 

 fluid, its body, below the vesicle, swells and soon opens up (figs. 

 68-76). The arms which are tucked around the nucleus unwind 

 rather quickly. At first fine ray-like lines make their appearance, 

 then the needle-like projections which form the ends of the rayed 

 arms. Soon the arms themselves are entirely released and they 

 uncoil in somewhat the manner of a watchspring. Figures 73 to 

 74 are top views of the spermatozoon showing the uncoiling of 

 the arms. As they uncoil a glue-like substance seems to diffuse 

 from them. This substance, undoubtedly, was the cement that 

 kept the arms coiled about the nucleus. 



In the uncoiled state the spermatozoon may be compared to a 

 floating amoeba (figs. 75-76). Figure 75 is a side view showing 

 the vesicle, V, on top, the nucleus, N, on bottom and the flagel- 

 lated arms, E, radiating out from the juncture of these two 

 structures. Figure 76 is a top view showing all these parts 



JOURNAL OP MORPHOLOGY, VOL. 25, NO. 4 



