18 H. M. WOODCOCK. 



zoiteSj or very young trophozoites (.starting originally from 

 tlie vascular system of the gut), then grow in situ and so 

 attain to the sporont phase? I think this is conclusively 

 negatived by the following considerations : 



(a) I have never seen a single C. minchinii in the vas- 

 cular system proper (i. e. the vessels and network attached 

 to the gut), or in any way connected with it. 



(b) I have never seen small forms in the connective tissue 

 around the muscle, and indeed, 



((•) I have never found tiny forms anywhere but in the 

 respiratory trees. 



(d) The distinct epithelial layer next to the parasites when 

 in this situation. No such cellular aggregation is ever found 

 around them while in the trees. 



(e) The frequently seen process of attempted invagination 

 ah'eady described represents the commencing stage of en- 

 cystment. No other explanation than the one above given, 

 namely that the animals are endeavouring to push into, and 

 are becoming enclosed by, the host's tissue, is possible.^ 



These fads lead one inevitably, I think, to the conclusion 

 that the parasites enter the respiratory trees directly from 

 the outside, and that many of them pass thence into the 

 ccelome,- and as soon as possible become attached to the 

 coelomic epithelium, either of the body-wall or of a connective- 

 tissue or muscle strand, where, after further growth, they 

 finally become encysted. 



I never observed any sporulating stages in the respiratory 

 trees, and so cannot say whether the Gregarines sporulate in 

 this position or not. I do not think those which have become 

 large and spherical in this position pass into the coclome. 



' Prof. Mincliin kindly looked at, several of my pre])aratioiis, which sliow 

 the process most clearly, and lie is equally of the opinion that the parasites 

 are entering and not emerging. 



^ Presumably the young forms always pass through llie wall of tlie tree into 

 tlie body-cavity, since any internal (ccelomic) openings of the former are 

 usually denied. 



