8G0 AUSTRALIAN HIRUDINEA, II , 



with the proboscis-like structure than with the oesophagus. 

 These capillaries are, however, by no means so abundautly or 

 strongly developed as in connection with the former. No 

 diverticula arise from the crop; and in this respect the genus 

 agrees with most other aquatic Herpobdellids, and differs from 

 the terrestrial members, such as Orobdella and Lumbricobdella. 



The intestine has its epithelium folded to such an extent that 

 it projects into the lumen as elongated villose structures. Sinuses 

 are very strongly developed beneath the epithelium, so that in 

 all probability ingestion takes place in this region. The canal 

 opens at the anus between the fourth and fifth annuli from the 

 posterior extremity. 



Reproductive organs. — The testes are arranged in the form of 

 capsules along the sides of the ventral sinus, and extending for a 

 short distance up the sides of the digestive canal. There are 

 about seven such capsules. Each testis contains a mass of 

 mature spermatozoa. The male ducts call for no special remarks. 



The ovaries are large hollow sacs situated midway between the 

 dorsal and ventral surfaces, each containing a large number of 

 ova which are apparently mature. The ova are large, and form 

 the most prominent cellular elements in this region of the body. 



Vascular system. — This system resembles that of Nephelis and 

 Trocheta, consisting of two lateral vessels, a median ventral 

 sinus, and numerous coelomic spaces carrying blood. 



(a) The lateral vessels are provided with an epithelium con- 

 sisting of minute cells which take a deep stain with hematoxylin. 

 Outside this lining layer is a well developed circular musculature. 

 These channels in all probability are contractile in the living 

 animal, as in the case of Nephelis and Trocheta. 



(b) The ventral sinus, in the single specimen available for 

 examination, was observed to be developed to the extent of 

 having a lumen not many times larger than that of the lateral 

 vessels. In its normal position it lies immediately ventral to the 

 digestive tube; but, in the neighbourhood of the posterior region 

 of the stomach, the digestive tube was found to be pushed towards 

 the dorsal surface, and the ventral sinus separated considerably 



