SEA-FISHERIES LABORATORY. 135 



They stain more deeply and brightly than the sporo- 

 blasts, and cannot be mistaken for these. Thelohan 

 does not describe them, and since mine are all ripe 

 cysts I have no means of ascertaining their origin 

 and significance. Passing inwards we come to clusters 

 of ripe spores, and these soon almost entirely 

 replace the endoplasm, and run together to form 

 the central mass of spores, the organellas themselves 

 having broken down and disappeared. Often, however, I 

 noticed, as it were, tongues of endoplasm projecting inter- 

 nally towards the centre, and in some sections appearing 

 as isolated patches, some of which were fertile, but others 

 apparently sterile. These are not to be confounded with 

 the islands of residual-tissue described below. Although 

 I have examined sections through many cysts, I have 

 not seen any instances of the degeneration of the spores 

 such as is described in the central part of " over-ripe " 

 cysts. In all mine, the central spores are as healthy in 

 appearance and as deeply-staining as those of the peri- 

 phery. A noteworthy difference in the central mass of an 

 A cyst from that of a B one, is the absence in the former 

 of the areas or patches which are the more or less colloidal 

 residua of the degeneration of tissue-cells, &c, of the host. 

 Moreover, the spores themselves in the former case are 

 quite free, and not embedded in any matrix. These facts, 

 together with those already set forth, emphasize the dis- 

 tinction which I wish to bring out between the two kinds 

 of cyst. "While the one (A) is practically all parasitic 

 tissue, and represents one individual, the other (B) — the 

 pseudocyst — is the consequence of the massing together 

 and circumscribing of (a portion of) an infiltrated area, 

 originally comprising many tiny, daughter, individuals 

 fof which, in an old pseudocyst, nothing is left save 

 spores) diffused in and among the host's tissue (also 



