128 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



The sexual organs are quite extensively developed, and periodically 

 obscure the remaining viscera. In the male the simple testis is situ- 

 ated in the second segment, and the single vas deferens, after numer- 

 ous windings through nearly the entire length of the body, opens at 

 the base of the first abdominal segment under a spined plate. A part 

 of the vas deferens is of a glandular character and secretes an elongate 

 tube, the spermatophore, which serves to contain the spermatozoids, 

 and is fastened by the male at the opening of the median pore of the 

 female; on contact with the water this tube, which is at first soft, con- 

 tracts and presses the contents into the opening of the female organs. 

 So long is the vas deferens that as many as three spermatophores are 

 sometimes seen in the body at once. The spermatozoids are very 

 small. The geniculated male antennae are used in grasping the setse 

 on the tail of the female, and the curiously modified inner branch of 

 the third foot of the male may assist in fastening the spermatophore 

 upon her body. The ovary occupies the same position as the testes, 

 and the two ducts are coiled in the body from end to end, opening in 

 the median pore behind the fifth pair of feet. When the eggs are 

 ready to be laid, they are forced out, carrying with them a film of the 

 secretion of the lower, glandular portion of the ducts, which is of a 

 collodion-like consistency, and which forms the inclosing sac. The 

 young become fully developed sexually before they assume their final 

 form, and it is not unusul to find ova bearing females which are not 

 only much smaller than the parent, but with considerable differences 

 in the various organs. 



This sort of heterogenesis is not uncommon among lower Crustacea, 

 for the young may differ much from the mother till after they have 

 themselves produced young. 



Four species have been recognized in America, of which one is cer- 

 tainly identical with a widely distributed European form, and a sec. 

 ond is probably identical with an English species. C imJustris Brady 

 seems to depart considerably from the norm of the genus and may 

 prove a type of a marine genus. No true Canthocaimptus is more than 

 accidentally marine. 



The ten species below enumerated are all that have fallen under 

 the author's notice, though others may have been mentioned. 



KEY TO THE GENUS CANTHOCAMPTUS. 



I. Inner ramus of the fourth foot two-jointecl. 

 a. Inner ramus of the first foot two-jointed. 



* 1.0 mm. long; b3sal joint of fifth foot small gracilis, 129 



** 0.5 mm. long; basal joint of fifth foot long brevipes, 130 



h. Inner ramus of the first foot three-jointed. 



* Inner ramus of the second foot two jointed. 



