96 University of California Publications in Zoology. [Vol.6 



substrata or menstrua (the tentacles, the branches of the ten- 

 taeles, the transverse blood sinuses of the branchial sac, etc.). 



3. Attention to these repetitive series makes it quite certain 

 that many of them, both of the genetic and of the simultaneous 

 series, not only are subject to definite schemes as to positional 

 arrangement and time of origin, but also as to mass relations. 

 Otherwise stated, the repetitive series which obviously constitute 

 so large a part of the whole animal are to a greal extent subject 

 to mathematically treatable order. 



4. A fairly extensive comparison of animals from the coast 

 of southern California with others very like them living in 

 Puget Sound. State of Washington, discovers certain consider- 

 able and constant differences between them (difference in char- 

 acter of test and number of tentacles). Those living on the 

 California coast need a group name to distinguish them from 

 those living on the Washington coast. As such name Halocynthia 

 joknsoni may be used, the Washington animals being called //. 

 Jiaustor. These two groups may be conveniently spoken of as 

 species. 



5. So far as the present inquiry has gone, the attempt to 

 find a causal relation, or a necessary correlation, between the 

 character differentials of the two species and their environmental 

 differentials, has produced negative results. In other words, 

 the results do not enable us to affirm anything more definite 

 about the adaptation of //. Johnson i to its environment than 

 that in a general way it is so adapted; that is. that it is suffi- 

 ciently adapted to enable the individual animals to live and 

 maintain their specific identity in a considerable range of envi- 

 ronmental conditions. 



