206 - BERTRAM G. SMITH. 



of differentiating the two species. The range of variation in 

 the length of the middle piece of A. punctatum (in several in- 

 dividuals) is 14 ;^- i6 /><; in ^. jeffersonianum (in one individual) 

 11.2/^-11.9/^. 



The fact that only one individual of A. jeffersonianum was 

 considered of course militates against the acceptance of these 

 results as absolutely conclusive; but since material was taken 

 from several individuals of A. punctatum, and in all of these 

 there was a decided difference from the results obtained from the 

 single individual of A. jeffersonianum, it is highly probable that 

 the species may be distinguished in this way. 



Spermatozoa were then taken from a dozen or more spermato- 

 phores, each from a different group and presumably deposited 

 by a different individual. This material was treated precisely 

 as in the case of the spermatozoa described above. Somewhat 

 to my surprise and disappointment, all the specimens conformed 

 to the dimensions of the sperm of A . punctatum. 



Structure of the Spermatophores. — ^Two general types of sperma- 

 tophores are recognizable: simple and compound. The com- 

 pound spermatophores may be roughly divided into the vertically 

 serial, and the Y-shaped types, the former by far the most com- 

 mon; but both these conditions maybe found combined in one 

 compound spermatophore. 



A spermatophore of the simple type is illustrated in Fig. i. 

 It consists of an expanded hummocky base and a stout stalk, 

 of very clear, transparent, gelatinous material, surmounted by 

 a dome-shaped mass of snowy-white seminal fluid. 



While to the naked eye the stalk of a simple spermatophore 

 is perfectly clear, under a low power of the microscope it is seen 

 to possess a delicate network of fibrous material. Under high 

 power this is found to be made up of sparsely distributed sperma- 

 tozoa, interlaced to form a mesh work. In some spermatophores 

 the strands of this network assume considerable regularity. 

 There may be distinguished regular parallel strands extending 

 in the direction of the axis of the stalk, distributed at about 

 equal intervals through its substance ; these strands are connected 

 by more irregular cross-strands. 



Evidently a few spermatozoa are present in the cloaca at the 



