296 NATHAN FASTEN. 



remains on the outside where it soon disintegrates. In order 

 to bring this mode of fertilization in harmony with the idea of 

 the continuity of the chromosomes, Binford suggests that "the 

 contents of the capsule (vesicles) may be derived from the nucleus 

 of the spermatid and is probably oxychromatin which deposits 

 basichromatin after it enters the egg and so gives rise to the 

 chromosomes in the male pronucleus." 



It is thus obvious that more research along this line is essential 

 before any definite conclusions regarding fertilization in the 

 Decapoda can be formulated. If we accept Binford's results 

 then we must admit that they are contrary to everything that 

 we know regarding fertilization in animals. 



SUMMARY. 



1. The spermatozoa of the black-clawed crab, Lophopanopeus 

 bellus (Stimpson) Rathbun, are minute, greenish cells, which 

 appear like spheroids when seen from the top or bottom and like 

 ellipsoids when seen from the side. 



2. The structure of these spermatozoa is very similar to that 

 of the edible crab, Cancer magister Dana. In the centre there 

 is a tube-like central body, and surrounding this in order of 

 sequence is a secondary vesicle, a primary vesicle and a nuclear 

 cup with slender radiating arms. 



3. There are four types of spermatozoa produced in Lopho- 

 panopeus belhis, depending on the number of radial arms which 

 they contain. There are three-, four-, five- and six-rayed sperma- 

 tozoa, with the four- and five-rayed types predominating in 

 numbers. 



4. In sea water and isotonic solutions of various salts, no 

 change occurs in the normal appearance of the spermatozoa. 

 In hypotonic solutions of these salts the spermatozoa explode 

 by an eversion of the two vesicles and the central body. 



5. In ovarian fluids some of the spermatozoa explode violently, 

 with a rupture and disintegration of one or both vesicles. 



6. Acidulated sea water has a harmful effect on the sperma- 

 tozoa, either causing swelling or shrinkage, with subsequent 

 disintegration. 



7. A lowering of the osmotic pressure in the medium that 



