548 Marsh—Structure of the Larva of Epischura Lacustris. 
exopodite is represented by the two outer segments, while the 
curved process of the basal segment is the endopodite. 
The fifth feet of Temora and Heterocope are in their structure 
very similar to Epischura , and it is probable that they should 
be explained in the same way. 
In regard to the inferences to be drawn from the structure of 
the abdomen and fifth feet as to the family history of Epischura , 
it is, perhaps, not safe to say much until the other parts of the 
body have been more thoroughly worked over. There seems to 
be nothing especially significant in the structure of the fifth 
feet, it is true that that there is a marked resemblance between 
the larval fifth feet of Epischura and those of Diaptomus , but it 
is no more than one would expect if they conform to the general 
type of structure in the copepod appendage. 
The persistence of the three large furcal setae, even in the 
earlier stages, would seem to indicate a rather- remote connec¬ 
tion with Diaptomus. On the other hand, the fact that the 
asymmetry of the abdomen and the lateral processes of the ab¬ 
dominal segments appear only in the very last stages point very 
strongly to the probability that this most marked peculiarity of 
Epischura is a recent development, and that Epischura may be 
quite closely connected with forms having symmetrical abdo¬ 
mens. 
Ripon , Wis ., October , 1899. 
