232 FERTILIZATION 



The B group of vitamins may be directly related to sperm motility. Other 

 substances, such as iron, copper, etc., are present. One should consider the 

 seminal plasma, therefore, as a most important association of substances which 

 aids in producing a protective environment for the sperm while the latter is 

 in migration to the egg. 



The importance of the environment of the sperm and also that of the egg 

 cannot be overemphasized. If normal fertilization is to be effected, optimum 

 conditions for both sperm and egg must be present. An example of this fact 

 is shown by the observations of Reighard on fertilization of the walleyed pike. 

 (See Morgan, '27, p. 18.) The best results with the eggs of this teleost fish 

 were obtained when the eggs were fertilized as soon as they entered the water 

 from the female genital tract. After two minutes only 40 per cent of the eggs 

 segment, and after ten minutes no eggs segment. For many fish, "dry fertili- 

 zation" gives the best results. Dry fertilization consists in stripping the female 

 to force out the eggs into a dry container and then stripping the milt (seminal 

 fluid) from the male directly over the eggs. The eggs are then placed in water 

 after a few minutes. This work suggests strongly that a deleterious environ- 

 ment for either the egg or the sperm is disturbing to the fertilization process. 



4) Roles Played by Specific Structural Parts of the Sperm in Effecting 

 Contact with the Egg: a) Role of the Flagellum. As indicated in the 

 foregoing paragraphs, when the sperm cells have reached the normal fertili- 

 zation site, the activities which bring about actual contact of the sperm with 

 the egg largely is a sperm problem. Aside from enzymes elaborated by the 

 sperm, sperm motility is extremely important in achieving this end. Although 

 sperm may appear to swim rather aimlessly, vigorous, healthy sperm do lash 

 forward more or less in a straight line for some distance; ill-developed or 

 otherwise impaired sperm may simply swim round and round or move forward 

 feebly. In the case of flagellate sperm, the structure which makes the forward 

 swimming movement possible is the flagellum or tail (figs. 74, 77, 78, 79). 

 A two-tailed sperm or one in which the flagellate mechanism is not well de- 

 veloped would be at a disadvantage in this race to reach the confines of the 

 egg. Brachet ('50) considers the rate of metabolism necessary to support the 

 activities of the tail or flagellum in sperm movement as directly comparable 

 to that of muscle. 



An interesting peculiarity of a different type of sperm mechanism useful 

 in achieving contact with the egg's surface is that of the so-called "rocket 

 sperm" of certain decapod Crustacea described by Koltzoff (fig. 75). After 

 attachment of the sperm to the egg by its tripod-like tips, the caudal compart- 

 ment, containing a centriole and the acrosome, explodes. "Koltzoff considers 

 that the force of the explosion drives the sperm upon, or even into, the egg" 

 (Wilson, '25, p. 299). 



b) Role of the Acrosome in the Egg-sperm Contact. The acrosome 

 of the sperm (fig. 78) has long been regarded as a structure which has a 



