130 University of California Publications. [zoology. 



pides, and that they become only secondarily united with buds. 

 Moreover, it seems probable that any bud may form a union 

 with an ovum, but that all such unions are not fertile, i.e., do 

 not produce embryos that give rise to larvaa. The view that 

 fertilization may take place at a time earlier than that at which 

 the ovicell is formed, and before the egg is surrounded by its 

 follicle, is supported by the facts given above. 



This brings us to the consideration of another possibility 

 which correlates the probable degeneration of the male cells 

 with a possible parthenogenetic development of the ovum. A 

 most careful and thorough search has been made through both 

 young and old portions of ovicell-bearing colonies for spermatozoa . 

 None whatever were found, although their size is not so minute 

 that they should be imperceptible with the high power of magni- 

 fication used. The possibility of parthenogenesis has already 

 been suggested by Smitt ("63), who, according to Claparede 

 ('70) had observed the asexual development of the egg in the 

 ovicells of Crisia eburnea and G. aculeata. Smitt's reason for 

 supposing that the ova of several species of bryozoa develop 

 parthenogenetically is mainly the failure to find spermatozoa. On 

 this point Claparede remarks that from Smitt's account it seems 

 probable either that the forms he reported upon are dioecious, 

 or that parthenogenesis may occur in the bryozoa under certain 

 circumstances. Of course, mere failure to find spermatozoa is 

 insufficient ground upon which to base a belief in parthenogene- 

 tic development, and as a matter of fact, one of the species Smitt 

 mentions, viz., C. eburnea, is dioecious. At the same time the 

 evidence here given of degeneration of the testis adds weight to 

 this suggestion, and the small number of spermatozoa compared 

 with the vigorous growth of testis is not only remarkable, but 

 may be correlated with the small number of ova that reach 

 maturity either partial or complete. It is possible that this 

 degeneration may be carried so far as to produce no mature 

 spermatozoa whatever, or so few that their role in the economy 

 of reproduction is reduced to the lowest degree. 



Iustances of the third class of ova (c), i.e., those that fail 

 of development, may be found in sections of the extremity 

 of a branch where ova are frequently found in various positions, 



