STATE GEOLOGIST. 



15 



page is growing obliquely upward. The Daphnidae are represented 

 as expanding upon the same plane as Moina, and the Lyncodaph- 

 nidae extend diagonally downward, producing the Lynceid branch 

 The Bosminidse spring from the stem at a lower point. These 

 relations are made obvious by the figure giving a view of the ideal 

 tree as seen from the side.* 



Limnosrefa 



Bowped/das \ 



Pseudosida 



y ^ — "^ 



Latona 



(?) 



V' ^Daphnella 



-^ v 



<srolDyE> 



I 

 I 

 r 

 - IVrO f N A Ceriodaphnia 



Simogephalas 



^Daphnia. 



<LYNCODAPHNID/E> 





Eosmma, 



StrebLocercus j^acrothn)! ^^ 

 laihnmira Drepanofhri>t^ 



^Sca'pholeheris 



Lyncodaphnia 





■ lliocrypius 



A cantholeberis 



5IDrD>E 



<LYNC^EID/E> f 



y, , Eurycercua ^^ J^^ 

 Camptocercu:s y o^ 



DAPHNIDffl 



Aionopsis^"' 



fAlona) y 

 Lynpeus 



(PleOcQxusI^ 



CbydorOs 



Graptojebris 

 ^MoQaspilus 



fig. 1. — table illustratilij'g the relation's of the 

 Cladocera Calyptomera. 



*NOTE.— To adapt the diagram to the theory that the Lyuceidse are the progenitors 

 of Cladocera, it is only necessary to revolve the imaginary line to the right, till it 

 coincides with the axis of that family. The question mark may be understood to 

 indicate that the source of the pivotal group, Moina, is uncertain. The author must 

 confess that his inclination is toward a belief that the line culminating in the Daph- 

 nidae diverged from a group of organisms resembling Phyllopoda, more definitely, 

 resembling Limnetes. There is a very remarkable resemblance between the larva 

 of Limnetes and Bosmina. The lateral spines of the former are, as will be shown 

 true homologues of the antennules of Bosmina. The later origin of the Phyllopoda 

 in their present form may be well admitted. 



1 Entomostraca, seu Insecta testacea, quae in aquis Daniae et Norwegige reperit 

 d«scripsit, etc. Otho Friedric Mueller, 1785. 



2 Monoc. qui se trouvent aux Envir. de Geneve. 



