216 EDWARD VAN BENEDEN, 



clear substance must be considered as forming the founda- 

 tion of this muscular layer, since where it thickens near 

 the anterior extremity of the body, on a level with the 

 transverse partition, the fibres no longer occupy the entire 

 thickness of the layer ; there the transverse fibrils are 

 really held in suspension in the transparent substance, 

 which in itself alone constitutes the entire partition. The 

 fibrils are not always found, at this level, near the cuticle 

 (figs. 2 and 3) ; sometimes the first fibrils envelope like 

 so many rings the posterior part of the anterior chamber 



(fig. !)• 



If, after having in some places torn the cuticle, the body 



of the Gregarine is slightly compressed, the contents flow 

 away, carrying here and there the muscular coating with the 

 fibrils it contains. These are then seen isolated, and it can 

 be perfectly recognised that these fibrils are composed of 

 small refracting corpuscles, elongated transversely, and very 

 close to each other (fig. 5) . After having by this proceeding 

 recognised the structure of the fibrils, I was able to see the 

 constituent corpuscles of these elements, in the living 

 Gregarine. For that, i-t is only necessary to slightly compress 

 it, and to examine the fibrils on a level with the nucleus of 

 the cell with a high power. At this point the granular 

 matter of the medullary column is replaced by a homo- 

 geneous and transparent nucleus, and it is fiir easier, aided by 

 this greater transparency, to distinguish the details on the 

 surface. 



If it were still possible to admit Dr. Bowman's ideas on the 

 structure of the striated muscular fibres of higher animals,^ 

 I would believe it possible to compare the muscular coating 

 of the Gregavina to a muscular fibre in its developing stage, 

 whilst it still shows in its central part protojilasm not 

 modified, and whilst the peri])heric part alone has been trans- 

 formed into a muscular substance. For at this time the 

 transverse discs formed by the juxtaposition of sarcous 

 elements are only simple rings, which may be compared to a 

 circular fibre of the Gregarinse. The clear and little re- 

 fracting fundamental substance of the muscular coating of the 

 Gregarina might be compared to the clear anfl monorefracting 

 layer of substance, separating, in a striated muscular fibre, 

 the discs formed by " sarcous elements.'''' 



We should suppose, in fact, that in a single cell the peri- 

 pheric coating of the protoplasm can become transformed into 

 muscular substance, as well as in a nucleated protoplasmic mass, 



' Bowman, 'On the Minute Structure and Movements of Voluntary 

 Muscles/ Loudon, 1840. 



