362 WHITMAN. [Vol. IV. 



into the ovisacs, and that fertilization takes place before oviposi- 

 tion, can be demonstrated by facts that admit of no doubt. The 

 passage through the wall of the ovisac — the only link in the 

 chain of direct evidence yet to be supplied — seems to be an 

 inference justified by all the known facts. Such a passage, in 

 the absence of any definite openings in the ovarian walls, would 

 have to be a forced one, depending upon the action of the 

 spermatozoa themselves. As these walls are represented by a 

 thin membrane which becomes enormously distended as the 

 eggs enlarge to maturity, the difficulty of penetration could not 

 be great ; and the case of Peripatus and the Turbellarians seems 

 to show that spermatozoa are capable of effecting automatically 

 such a passage. 



The view here taken finds a very strong confirmation in the 

 fact that precisely the same mode of copulation occurs in many 

 Turbellarians, in the Rotifers, and in Dinophilus, as the cita- 

 tions from Lang, Plate, and Harmer, given farther on, fully 

 show. The indications are that it occurs also in many oligo- 

 chastous annelids, as well as in several genera of leeches besides 

 Clepsine, — perhaps in all the Rhynchobdellidae. The occur- 

 rence of such a mode of copulation among so many of the lower 

 bilateral animals appears not only to render explicable the pluri- 

 penial condition of many Turbellarians and some of the higher 

 worms, but also to clear up many puzzling observations in regard 

 to fertilization in animals that have no intromittent organ. It 

 is no longer necessary to suppose that the spermatophores found 

 attached to different parts of the body of Peripatus must be 

 carried through the vagina and up the uteri in order to reach 

 the eggs ; and the discovery of spermatozoa projecting through 

 the ovarian walls of this animal, as reported by Moseley and 

 Sedgwick, ceases to be so complete a mystery. The difficulties 

 in the way of understanding how spermatophores can be of any 

 use when attached at a considerable distance from any genital 

 pore, and completely closed externally, as described by Vej- 

 dovsky for many annelids, may not be so great as they have 

 hitherto appeared. 



The facts and bibliographical notes to be presented in this 

 paper are sufficient, I think, to make it at least probable that 

 the original function of the spermatophore was precisely what 

 it now is in the Turbellarians, the Rotifers, Dinophilus, and 



