796 



FRESH-WATER BIOLOGY 



skeleton of whorled radiating spines. The efferent duct leads 

 to a tube, the vas deferens, which in turn leads to the penis 

 (Fig. 12460). 



These forms may also be propagated from unfertilized eggs, i.e., 

 by parthenogenesis. In such cases there may be a sexual genera- 

 tion followed by a number of such parthenogenetic generations. 

 Again, in some forms males have never been discovered, even 

 after as many as 18 years of continuous observation by very carer 



a 



FIG. 1246. CyprinotusdentataSha,rpe. (a) Penis, X 210; (6) Efferent or ejaculatory apparatus; (c) Cross- 

 section of same, X 293; (d) Part of a spermatozoon, X 525; (e) Right maxillary palp of male, X 

 158; (/) Left palp of same; (g) Extremity of testicular tube, showing spermatocysts, X 120; (h) Ma- 

 ture spermatocysts, X 120. 



ful observers. Herpetocypris reptans is a good example. Thus 

 some authors distinguish four types of the method of propagation, 

 as follows: 



1. Always sexual as in Notodromas monacha, Cyclocypris laevis, 

 Cypria ophthalmica. 



2. Temporarily parthenogenetic, as in Candona Candida, Cypri- 

 dopsis mdua. 



3. Locally parthenogenetic, as in Cypris incongruens. 



4. Always parthenogenetic, as in Herpetocypris reptans. 



