74 GARDINER. [Vol. XV. 



give convulsive struggles as if to rid itself of its annoyer and 

 swim rapidly away. Such individuals, when killed immediately, 

 showed in sections spermatozoa adhering to the back and 

 penetrating the tissues. In several of these specimens the 

 surface of the back where the spermatozoa were en masse was 

 slightly abraded. Whether or not this abrasion was caused 

 by the action of another individual or was due to accident is 

 uncertain. It seems probable that the numerous chitinous 

 "mouth pieces," which are one of the characters on which 

 Mark (i) has founded the genus Polyclioerus, may be used by 

 the animal to pierce the skin of other individuals so that sper- 

 matozoa deposited thereon may penetrate. The penis of this 

 form is unarmed, and is situated a short distance behind these 

 " mouth pieces," to which no definite function has hitherto 

 been attributed. That this is the normal method by which fer- 

 tilization is effected in this species I have no doubt whatever, 

 and believe it is but another case of hypodermic impregnation 

 to be added to the long list cited by Whitman (2) in his paper 

 on this subject. In no case, except when intertwined and 

 dying in stale water, have I seen two individuals bring their 

 ventral sides in contact as would be necessary in copulation. 

 In this group fertilization always takes place before the ova 

 are laid, and Dr. Sophie Pereyaslawzewa (3) states that in all 

 cases the polar bodies are formed while the ova are still in the 

 parent. That this is normally the rule in this species will be 

 shown later. 



In specimens examined under the slight pressure of a cover 

 slip it is easy to determine whether or not the eggs have been 

 laid, for when present they can be distinctly seen each with 

 its large round germinal vesicle. Very frequently, however, 

 instead of the germinal vesicle, a clear, translucent, dumb-bell- 

 shaped structure, which occupies the greater portion of the 

 ovum, may be seen. This is the amphiaster of the first seg- 

 mentation spindle, which in this species is usually formed 

 before oviposition. This is, however, not an invariable rule, 

 for I have found, in normal egg capsules, ova with round, intact, 

 germinal vesicles. In such cases, when the polar bodies are 

 formed they are always extruded from the egg, while when 



