376 University of Calif ornia Publications in Zoology. [VOL. 6 



IV. CHARACTERISTICS FOR SEPARATION OF SPECIES. 



The characteristic peculiarities of each species have been set 

 forth by its discoverer, but there has been no systematic attempt 

 to assess the worth of these characteristics for the genus as a 

 whole since that of Braun (1894). He was not acquainted with 

 at least one very important set of species characteristics, that 

 proposed by Haswell (1902). 



The first species characteristics were proposed by Diesing 

 (1859). He distinguishes G. rugosa from G. urna by the pres- 

 ence of lateral frills and spines and the greater size of the tail 

 rosette in that species. 



Monticelli also recognizes these two species, separating them 

 by the following points : 



1. The absence in G. rugosa of the frilled lateral margins. 



2. The greater length of the uterus in G. rugosa, possibly cor- 

 related with the following character. 



3. The presence of hooks in the embryo within the uterus of 

 G. rugosa. 



Braun (1894) recognized G. urna and G. rugosa, but only as 

 doubtfully distinct. The basis for separation he finds in the 

 position of the opening of the vagina and penis; the former 

 being the more anterior in G. urna, the latter in G. rugosa. 



Haswell (1902) recognized G. urna and G. rugosa and tenta- 

 tively proposed a new species, G. nigrosetosa. He distinguished 

 G. rugosa from G. urna on the following grounds : 



1. Relative position of the apertures of penis and vagina. 



2. Presence of an eversible cirrus adapted to self-impregna- 

 tion in G. rugosa. 



3. Spinules lining the ejaculatory duct in G. urna. 



4. Presence of hexacanth embryo in the uterine egg of G. 

 rugosa. 



5. Shape of spines. 



G. nigrosetosa he distinguishes on the following grounds : 



1. Size of eggs, 0.08 mm., as distinct from eggs of G. rugosa, 

 0.1 mm. 



2. Presence of operculum, distinct from G. rugosa and G. 

 urna. 



