ENTOMOSTRACA OF MINNESOTA. oat 
In the adult Cypris Herricki the caudal margin of the shell is entire. 
But in stage A, the caudal margin of the shell is bordered with minute 
teeth (Fig. 34). In this stage the teeth are quite small and might 
easily be overlooked; but in stage B (Fig. 35), these teeth have become 
very conspicuous. Indeed, they are the characteristic feature of the 
shell. These teeth are present throughout stages A to D, but in stage 
D they have begun to disappear. In the adult stage there is no trace 
of these teeth. 
A careful study of the adult shows that the shell is covered with 
hairs. These hairs are very conspicuous in stage A. The shell of the 
adult is marked with very conspicuous dark bands. 
An effort has been made to discover at what period these bands 
appear, and to see if they conform to the rules laid down by Professor 
Eimer. The characteristic bands on the shell may be present in any 
stage from A to the adult; and when they are present they do not differ 
essentially from the markings on the adult. The chief points of dif- 
ference being variations in the width of the bands. In all examples 
of stages Cand D examined, these characteristic markings were found; 
but in stages A and B, they were occasionally absent. An examination 
of Fig. 35 will show that some of these bands are longitudinal while 
others are oblique. 
Professor Eimer has attempted to establish the following rule for 
the formation of oblique markings on animals.* Oblique markings 
first appear as longitudinal lines. These lines become resolved into 
dots, these dots, in turn, rearrange themselves in oblique lines. If 
these laws were applicable to the markings on Oypris Herricki, in 
stages A and B, where we have some specimens with bands and others 
without them, we ought to find some transition stages—some stages in 
which the oblique markings were represented either by parallel lines, 
or by series of dots. But such is not the case. The shell is either un- 
marked by bands, or both oblique and longitudinal bands are present. 
As stated above, in stage A the appendages have practically as- 
sumed their permanent form. The post-abdomen is a notable excep- 
tion. This appendage is quite rudimentary; not only has it not yet 
acquired the typical number of set, but the longest terminal seta is as 
long as, or longer than, the remainder of the post-abdomen. This 
great relative length of the terminal seta is due, not to an over-devel- 
opment of the seta, but to an under-development of the body of the 
post-abdomen. That the post-abdomen appears to be the last append- 
age to development is rendered more striking by the discovery of C. 
_ Claus that the post abdomen appears before the formation of the sec- 
es ae. 
Stree = Pare y 
*G, H. Th. Eimer. Organic Evolution as the Result of the Inheritance of ee Characters 
According to the Laws of Organic Growth. Translated by J. T. Cunningham, 1890, P.7 
