— Il- 

 ls plainly visible, each rod being seen as a rhomb in the 

 section. Between the rods there seems to be some kind of a 

 weakl}^ stainable snbstance. The picture just described is most 

 frequently met with, and 1 consider it as normal. Very rarely 

 there are to be found sacs of Sarcocystis in which the rods, 

 or prisms, are arranged not diagonally, but in longitudinal 

 rows, parallel to the long axis of the sac (fig. 4). In transverse 

 sections the rods of such sacs seem to be flattened in the 

 direction of the long axis. 



I am inclined to regard the observations described in the 

 following manner. I suppose that the rods of the membrane 

 of Sarco spori di a are on the same time pretty soft, and 

 very elastic; the shape of the rods and their arrangement 

 vary and depend on the different degrees of contraction 

 of the muscle cell in which the parasite is imbedded. At an 

 average degree of contraction of the muscle cell the rods, or 

 prisms, have a rhombic shape, and are arranged normally, 

 i. e. in diagonal rows. At a strong contraction of the muscle 

 fibre the sac of the parasite is pressed in the direction of 

 the long axis. On account of this, the rods are displaced, and 

 become arranged into longitudinal rows, and the more or 

 less regular rhombic prism, or rod, is transformed into a 

 narrow plate the flat sides of which are directed to the ends 

 of the sac. When the contraction of the muscle cell is 

 relaxed, the rods again return to the same position and 

 assume their normal shape. Thus, the form and arrangement 

 of the rods of the membrane present a sort of function of 

 the degree of contraction of the muscle cell in the host. 



Out of all the preceding investigators the most correct 

 interpretation which is the nearest to my own of the membrane 

 in Sarcosporidia was given by Vuillemin (1902) who 

 studied Sarcocystis tenella. But, unfortunately, his brief paper 

 passed quite unnoticed, most probably on account of its brief- 

 ness and absence of drawings. Vuillemin also states that the 

 exterior layer of the membrane in Sarcosporidia consists of 

 prismatic rods, but he did not succeed in revealing the chan- 

 ges in their arrangement and shape as described above. 

 Vuillemin considers the rods to be irregularly angulous, 

 although he remarks that they are set into more or less re- 

 gular rows. Of the more recent authors only Ferret (1904),. 

 who made a special study of the structure of the membrane in 



