498 ON TWO REMARKABLE SPOROCYSTS, 



The Sporocysts (figs. 1 and 2) reach a maximum length of about 

 3 mm. They are able to creep about by alternate elongations and 

 contractions. During these movements the shape necessarily^ 

 varies greatly, but a "head," directed forwards, in locomotion, is 

 always recognisable, being constricted off as a rounded knob. As 

 Braun (3) points out, it is erroneous to refer to this as a sucker. 

 The muscular layers in this position are not thickened or modified 

 in any way. At its apex this is capable of being deeply involuted, 

 the result being the development of a pit with a terminal opening. 

 Since it is usually in this position that the fully developed 

 Cercaria escapes, an actual perforation sometimes is found to 

 occur, but this is of an entirely temporar}^ character. 



In many cases, applied to the outer surface of the Sporocyst 

 were groups of amoeboid cells emitting pseudopodia. Such groups 

 of cells are stated by Biehringer to occur generally in the Sporo- 

 cysts studied by him; the cells, which are blood-corpuscles of 

 the host, eventually giving rise to a layer — " the paletot "— which 

 completely invests the parasite. Such a continuous layer I have 

 never found. The groups of cells were never found in entire pre- 

 served specimens or in sections, having always become detached, 

 apparently'', in the process of preparation. 



The Sporocyst is enclosed in a non-cellular cuticular laj^er in 

 which no trace of nuclei occurs. This la3'er, which is 0'003 mm. 

 in thickness, exhibits a fine vertical striation, the significance of 

 which will be referred to presently. Beneath it are the layers of 

 muscle, which are extremely thin, an outer layer of circularly 

 and an inner of longitudinally running fibres. 



The outer layer (cuticle of most authors) is described as a thin 

 structureless membrane. Biehringer (2), Heckert {teste Braun) 

 and Loos (9) describe it as containing, in the young condition, 

 sparsely distributed nuclei. In the Sporocyst from Mytihis latus 

 nuclei were not found in the cuticle of any of the numerous 

 specimens which were examined for them : it is possible, however, 

 that the same may not hold good of those Sporocysts that are 

 developed directly from the Miracidium embrj^o. In the Sporo- 



