2o8 General Notes. [February, 



{^From the American Naturalist ^ February, i88j. ) 



Heterogenesis in the Copepod Crustacea. — In a former paper 

 we have considered examples of heterogenesis furnished by the 

 Cladocera. Let us now turn our attention to the copepods, the 

 Cyclopoiclea^ with the view to discover if similar conditions exist 

 here also. 



The standard books upon the non-parasitic forms of the Cope- 

 poda by Claus^ and Brady^ enumerate many species, but do not 

 agree entirely in synonymy, nor does it seem probable that, Claus, 

 who alone has done most of the anatomical and embryological 

 work in this section, has followed the life-history of anything like 

 a large proportion of the species named. 



It has been long known that the marine forms of Copepoda have 

 a very extended geographical range, many of them seeming to 

 complete the circuit of the earth's longitude and to extend over 

 several zones of its latitude^. Similar and often identical forms 

 occur in the Mediterranean and North seas, over all Europe and 

 the British Isles. Certain genera, as Calanus and Chetochilus, 

 seem to extend through all degrees of latitude from the equator to 

 the most northern seas. 



A confirmation of these facts may be sought in the works of 



^ C. Clans : Die Frei Lebenden Copepoden. T>eipsig, 1863. 

 2 G. S. Brady : Copepoda of British islands, Roy. Sec. 1878-9. 

 "* Claus ; Op. cil., pp. 83-86. 





