1888.] AUSTRALIAN CLADOCERA. 31 



has the carapace somewhat narrower, owing to the dorsal edge 

 being far less arched. It is, moreover, easily distinguished from 

 equal-sized female specimens by the structure of the antennulae 

 and the 1st pair of legs. 



The antennulae are comparatively much larger than those 

 in the female and somewhat less curved. They are moreover 

 distinguished by the presence of a rather strong finely ciliated 

 seta, affixed to a notch in the anterior edge, at some distance 

 from the base. 



The 1st pair of legs are armed with a rather elongate .in- 

 teriorly curved hook, projecting beyond the inferior edges of the 

 valves. 



The testes, easily observed through the pellucid shell, have 

 the form of 2 elongate saccular organs, irregularly instricted at 

 short intervals, and filled with a finely granular whitish content. 

 They partly cover the sides of the intestinal tube and have their 

 outlet at the tip of the tail. 



As to colour the body is very pellucid, with a faint grayish 

 or yellowish tinge, changing in adult females to a slightly orange 

 hue. The ephippia are of a rather dark-greyish colour and much 

 less pellucid. Within the body generally are dispersed nume- 

 rous small oil-globules of a bright reddish colour, more especially 

 along the intestinal tube. 



Biological Observations. — I first noticed the presence of 

 this form in the beginning of July 1886, in two of my aquaries, 

 prepared about the middle of the preceding month. The speci- 

 mens were at that time not very numerous, but in the course 

 ot the following days they rapidly increased in number. In 

 another aquary, arranged the 26th June, I likewise found, on 

 my return from an excursion in the beginning of September 

 same year, numerous specimens of this form, both males and 

 females, the latter mostly provided with ephippia, and on exa- 

 mining the bottom-residue of this and the two other aquaries, 

 numerous detached ephippia. each containing a brownish-coloured 

 winter-egg, were detected, evidently deposited in the mud during 

 the course of the summer. In one of the aquaries I allowed the 



