ANNELID GENUS CAMBARINCOLA — HOFFMAN 295 



species, greatly reduced jaws, moderate to elaborate development of 

 segmental ornamentation, and extreme enlargement of the prostate 

 both with respect to its size in comparison with the spermiducal 

 gland, and as regards the great size of the individual cuboidal cells. 



Critics of a narrowly defined genus might object that Pterodrilus 

 differs less from the Philadelphica section of Cambarincola than the 

 latter does from the Mesochorea section. But this is a matter of 

 personal preference, and something which must be settled by the test 

 of future usage. The recognition as a genus of a specialized offshoot 

 of some diverse genus has ample historical precedent. The lizard 

 genus Uta is generally recognized as only a modification of one of 

 the groups of Sceloporus, and doubtless a long list of similar evidence 

 could be marshalled in support of the Pterodrilus-Cambarincola 

 relationship. 



Unfortunately, as regards other genera, relationships are not so 

 clear. The tendencj^ toward development of an eversible (and 

 ultimately an extrusible) penis seems clearly a specialization, but 

 one which had perhaps been achieved independently and at different 

 times. Within the group of genera which are so endowed, there 

 exists considerable variation as regards presence or absence of the 

 prostate, modification of the ejaculatory duct, and modification of 

 the spermatheca. Since these genera are composed largely of very 

 small worms, with every indication that a great many remain to be 

 found and studied, it would be premature to venture any opinion on 

 their affinities. 



"^Vhether the genera Triannulata and Stephanodnlits (the latter in 

 the sense of Goodnight's usage of it for a Californian species) differ 

 from Cambarincola is something which remains for future settlement. 



Phylogenetic Considerations 



The following remarks constitute an attempt to summarize the 

 inferences which can be reasonably drawn from our present state of 

 knowledge of the genus Cambarincola. It seems relativel}^ safe to 

 assume that probabl}^ most of the more common species of the genus 

 have been described, although a number of localized forms undoubt- 

 edly remain to be discovered. 



Some criteria have been set up for the evaluation of certain diag- 

 nostic characters against the standard of a hypothetical ancestral 

 condition (cf. pp. 281-291). On the basis of these criteria, it is possible 

 to consider some species as primitive and some as specialized in the 

 two largest sections of the genus. By restricting comparisons to 

 the members of a given section, rather than the genus as a whole, 

 we find that the presumptive conservative forms tend to be scarce, 



