﻿Notes upon a Haplosiooriclian. 



181 



parasite already noted appears to be as follows: — The animal 

 increases in size, the nuclei dividing simultaneously by an 

 apparently very simple method of mitosis. Eound the 

 parasite there begins to be formed a nodule of connective 

 tissue, which shows the typical concentric layer appearance 

 so often found in cases where a parasite is invading the 

 tissue of a vertebrate host. As far as the nodule of con- 

 nective tissue is concerned, some of these earlier stages 

 exactly recall the similar concentric nests formed round 

 certain tissue-inhabiting nematodes. The parasite and the 

 nodule both increase in size, and the former gradually 

 secretes the gelatinous cyst-wall already mentioned. 



After a time the Icthyosporiclium begins to quit its cyst 

 (Figs. 3 and 7). It is rather difficult to determine precisely 

 what conditions the exit of the parasite. It is very 

 probable that the increase in size overcomes the tenacity 

 of the envelope. Occasionally oval or oblong cysts are 

 met with, apparently indicating that the increase in size 

 of the parasite has stretched the capsule unequally. The 

 actual size of the animal seems to have nothing to do 

 with its quitting the cyst. Parasites of very varying sizes 

 may be found in the act of creeping out, if a sufficiently 

 large amount of material is carefully searched. The most 

 usual method of exit is for the animal to push out one 

 part of the cyst-wall in a more or less broad process, — 

 sometimes this outpushing may be shaped like a finger, 

 or may form quite a wide bay. The outermost layer of 

 the cyst-wall bursts first, but the inner parts seem to be 

 more elastic, and still ensheath the protoplasmic body. 

 The whole parasite may become very elongated, though 

 without any very marked increase in size taking place. 

 The inner part of the cyst may now rupture also, and the 

 naked parasite appears to slip out among the tissue of 

 the nodule. Completely empty cysts are quite often met 

 with, some of them showing precisely the same shape as 

 that in Fig. 7, which here still encloses the parasite. Some- 

 times the inner part of the cyst-wall stretches to a much 

 greater extent than shown in this figure, but there seems to 

 be a great deal of variation. While this is one quite typical 



