84 H. M. WOODCOCK. 



(3)^ Diplodiua irregularis lives either iu the lumen of, 

 or attached to, the blood-vessels. There is no definite relation 

 between the growth, or period in the life-history, of the 

 animals and the time of their evagination of the wall of the 

 vessel. They may either come out when quite minute, or, 

 on the other hand, they may commence sporulation while still 

 in the lumen. The parasites, whether as trophozoites or as 

 cysts, are never free in the coelome. The cysts are most 

 probably ruptured iu situ, the liberated spores escaping 

 when some Cuverian organs are extruded. 



The habitat of D. minchinii is very varied. The para- 

 sites are most numerous in the wall of the respiratory trees. 

 They also occur attached to the coelomic epithelium of the 

 body-wall, of the retractor muscles, and of various more or 

 less vascular strands which cross the body-cavity, chiefly in 

 the hinder part. They are never iu, or in any way related to, 

 the vascular system proper in connection with the gut, and 

 obviously do not reach the site of infection by way of the 

 mouth and intestine, as does the other species. All the 

 evidence points to the conclusion that the spores enter 

 the host through the cloacal aperture, being sucked up by the 

 iiihalant current into the trees. 



The parasites in the coelome are always partly covered by 

 a double layer of epithelium, the inner one being really an 

 invagination of the outer one. There is not the slightest 

 doubt that the animals are passing in and not emerging. 

 The process is the reverse of the evagination process met with 

 in D. irregularis. The later stages constitute more an 

 overgrowing and surrounding of the parasite by the epithelium 

 and connective tissue of the host than an actual in pushing on 

 the part of the Gregarine itself, which only larely occurs to 

 any extent. The parasite becomes at length completely 

 encysted and ready for sporulation. 



(4) The gregariniform adults of both species are perfectly 

 regular in form and typically ovoid. They are quite motion- 

 less. Each adult is really a '^ couple," Diplodina being a 

 ' Tlic nuniberb icier to the concspoiuliiig sections. 



