SPERMATOGENESIS OF CANCER MAGISTER. 293 



5. OPENING OF THE MATURE SPERMATOZOA. 



The mature spermatozoa within the spermatophores are dor- 

 mant structures, but when they are removed from the sper- 

 matophores and placed in fluids whose concentration is less than 

 sea water, they undergo interesting changes. In many ways 

 these are similar to the changes which Binford ('13) describes for 

 the spermatozoa of Menippe mercenaria. 



The method employed in studying the opening of the mature 

 spermatozoa of Cancer magister was similar to that employed by 

 Binford ('13). Numerous spermatophores suspended in either 

 crab's body fluids, or sea water, were placed on a slide and covered 

 with a cover-glass. By applying pressure to the cover-glass 

 many of the spermatophores were ruptured, thus liberating the 

 spermatozoa. These could then be examined under the high 

 powers of the microscope. By allowing numerous salt solu- 

 tions, already mentioned under the section on 'Materials and 

 Methods,' to diffuse under the cover-glass, all of the changes in 

 the opening up process or the so-called explosion of the sperma- 

 tozoa could be followed out quite accurately. Many of these 

 spermatozoa in various stages of their explosion were fixed and 

 stained on the slides and were then used for later study and com- 

 parison. 



In the crab's fluids, in sea water, or in solutions of NaCl, KC1, 

 CaCl 2 , NaNO 3 and KNO 3 which are isotonic with sea water, 

 almost no change occurs. Usually the rays of the nuclear-mito- 

 chondrial cup unravel, revealing spermatozoa which contain 

 either three (Fig. 68) or four (Fig. 69) rays. In hypotonic 

 solutions of the last-mentioned salts, the spermatozoa undergo 

 an explosion, and change considerably in appearance. Osmotic 

 pressure, undoubtedly, accounts for this explosion as was sug- 

 gested by Koltzoff ('06). 



The first step in the explosion of the spermatozoa is the extru- 

 sion of the second vesicle. This vesicle normally surrounds the 

 central body and is embedded in the first vesicle (Figs. 70 and 

 71). When the second vesicle begins to extrude, it swells some- 

 what (Figs. 72-76, v'} in size and at the same time it stretches 

 the upper portion of the first vesicle and makes it appear like a 

 thickened ring (Figs. 72-76, s). Simultaneously with this, the 



