1888.] AUSTRALIAN CLADOCERA. 13 



The heart, located dorsally in the most anterior part of the 

 trunk, is remarkable for its large size and bag-shaped form. It 

 is somewhat curved, with the upper edge distinctly concave, the 

 anterior extremity being broadly truncate, whereas the posterior 

 is rounded. On either side, about in the middle, a very distinct 

 transverse venous opening occurs, limited by two movable lips, 

 and numerous exceedingly delicate muscular fibres are arranged 

 in the walls of the heart concentrically to this opening. 



The ovaries have both as to place and structure the greatest 

 resemblance to those organs in other Sididse. The ova, when 

 recently deposited into the matrix, exhibit a bright greenish vi- 

 telline substance, subsequently divided into large cellular globules. 



The whole animal is very pellucid and almost colourless, 

 with no trace of the gorgeous pigment adorning the valves in 

 full-grown specimens of Latona setifera. 



Biological Observations. — The first specimen of this remark- 

 able form I observed on the 21st June 1886 in a small aquary 

 prepared on the 7th of same month. The said specimen was an 

 adult female, with the matrix greatly distended with numerous 

 embryos in a rather advanced state of development. By the aid 

 of a dipping-tube I succeeded in fishing up the specimen for exa- 

 mination under the microscope, when it at once proved to be a 

 very interesting new form. Being anxious to allow the specimen 

 to deposit the young brood, for this once I confined myself to 

 merely making a slight sketch of the animal, whereupon it was 

 immediately replaced in the aquary. Early the following mor- 

 ning I was placed before the aquary in search of the specimen. 

 But nowhere was any trace to be detected of its existence, and 

 I began to fear, the specimen had not endured the treatment 

 necessary for its preliminary examination and had succumbed 

 along with all its progeny. Some hours later in the day. when 

 examining the aquary in question, I was, however, most agree- 

 ably surprised by catching a glimpse of the animal darting 

 about in the water for a moment, and then hiding itself for some 

 time, so as to be quite invisible. The following days I repeat- 

 edly watched the animal and observed its peculiar habits, in 



