STUDIES ON CEYLON H.EMATOZOA. 751 



in fig. 19 strongly suggests that it lias had an enclo-corpuscular 

 existence. I have nevei* seen any sign of the parasite reach- 

 irig the lung by being engulfed by leucocytes, and I am there- 

 fore inclined to think that the schizonts in the lung must 

 have come from the blood-corpuscles. 



IV". Stages in the Leech. 



Before giving an account of the stages of Haemogregarina 

 nicoriee observed in the leech, it will, I think, be well to 

 describe the more important features of the leech itself. 



The form in question belongs to the Rhyuchobdellid genus 

 Ozobran chus. Mr. W. A. Harding, to whom tlie leech was 

 sent for identification, found that it belonged to a new species, 

 and called it Ozobranchus shipleyi. It is a small aquatic 

 form carrying a row of feathery gills on each side of its body. 

 The creature rarely reaches more than about one third of an 

 inch in length even when fully extended. Generally speaking, 

 it is found attached to the tortoise at the back of the neck, 

 round the sockets of the limbs, and more rarely upon the 

 ventral side near the throat. The leeches have a tendency to 

 assemble together in groups — a habit they preserve even when 

 kept in a glass dish. The gills of the Ozobranchus are kept 

 in constant motion, and the animal dies if left out of water for 

 any length of time. I was not very successful in getting the 

 leeches to live for long in captivity, nor was I able to discover 

 exactly what was amiss in the conditions to which they were 

 exposed. Possibly the smaller quantity of water rose to too 

 high a temperature. Leeches nre usually very hardy and live 

 well in captivity. I had no difficulty in keeping Poecilob- 

 della alive in Ceylon for months. I have often observed, 

 however, that newly fed specimens are much less resistant 

 than fasting individuals, and this seems true of a number of 

 different species of leech. Almost all the Ozobranchus I 

 got were either in the act of feeding or newly fed, and there- 

 fore in the least favourable condition. This leech seems to 

 show a much closer adaptation to its host than generally 



