STRUCTURE OF THE GREGARIN.E. 217 



really formed by the fusion of a certain number of cells. But 

 the last works of Krause,^ Hensen,^ Flos;el,^ and Merkel/ 

 on the structure of striated muscular fibre have so much 

 modified our ideas on the organization of these elements, they 

 have shown to us so complicated a structure in these fibrils, 

 that all assimilation of the muscular fibres of the Arthro- 

 prod and the Vertebrata to the muscular mechanism of the 

 Gregarine, appears to me now impossible. It is only by 

 comparing the muscular fibrils of the Gregarina with the 

 fibres of Infusoria that the meaning which I have given to 

 these elements appears to me justifiable. 



To finish the description of the Gregarina it is necessary 

 to say something more as to the contents of the anterior or 

 ce])halic chamber. These contents are always very granular 

 and very opaque, at least in the central part of the chamber. 

 The refracting granules that this part of the body contains 

 are remarkable for their pretty considerable size, and by the 

 ease with which, under the influence of an increasing pres- 

 sure, they fuse one into another, and form thus irregular 

 piles of a highly refracting substance. 



When the Gregarina reaches its complete development, 

 notwithstanding its monocellular nature, it appears to us 

 then to be a being with a rather complex structure. As in 

 pluricellular organization, the division of physiologic work 

 brings about the differentiation of the cells and the progres- 

 sive complication of the organization, so, in the same way, 

 this principle of the division of work brings about in certain 

 monocellular beings a local differentiation of the protoplasm, 

 and causes the formation of distinct organs. 



In the Gregarine such are the cuticle, the muscular layer, 

 the cortical substance, the medullary column, the trans- 

 verse partition, and the cephalic chamber. All these parts 

 are but the result of the slow transformation of the proto- 

 plasmic body of the young Gregarina; progressively the 

 different layers show themselves during the course of the 

 autogenic evolution ; it is also at a relatively advanced epoch 

 of development that a transparent partition appears between 

 the anterior extremity of the body, characterised from the 

 beginning by ani accumulation of refracting globules, and 

 the posterior chamber. All these modifications are produced 



> Krause, ' Zeitschrift fiir Ratioiinelle Mediziu,' iii Beitsc, 33 Bd., p. 

 2G5. 



2 Henseii, ' Arbeiten des Kieler Physiol. Institut/ 1868, p. 1. 



3 Flogel, ' Archiv fiir Microsk. Anat.,' Bd. 8, 1 Lief. 



4 Mei-kei, ' Archiv fur Microsk. Auat.,' Bd. 8, 2de Lief, p. 244. 



