STUUCTURE OF THE GREGARIN.E. 215 



is found between the cuticle and the cortical parenchyma. 

 It is about as thick as the cuticle ; it enlarges slightly at the 

 anterior extremity of the body, and it is this that is 

 inflected to constitute the transverse partition which sepa- 

 rates the anterior from the posterior chamber. This layer 

 is developed on the whole surface of the posterior chamber; 

 but it stops a little in front of the partition of separation 

 between the two chambers, so that the cephalic chamber is 

 only covered on its posterior face, and on a small part of 

 its lateral face by the layer of which we are speaking. 



It consists of a colourless substance, homogeneous and 

 transparent, formed by transverse fibrils, composed of a very 

 refracting substance ; these present all the appearance of the 

 muscular fibrils of Infusoria. These fibrils form either cir- 

 cular rings or a continual spiral developed on the whole 

 surface of the Gregarina ; but they are wanting in the 

 transverse partition, which is exclusively composed of a 

 transparent colourless substance. 



If we examine the surface of the body of a Gregarina 

 with a high power (obj. 9 or 10 immersion of Hartnack) in 

 the intestinal liquid of the lobster, or in the serum of its 

 blood, we distinguish a transverse striation (very evident) 

 in the sub-cuticular layer (fig. 1). These dark striations 

 are very near each otlier ; they are placed with perfect regu- 

 larity always equidistant, and they are nearly as evident as 

 the transverse striation of the muscular fibres of an Arthropod 

 or a Vertebrate. They become still more distinct under the 

 influence of acetic acid, chlorhydric acid, or a Aveak solution 

 of osmic acid. 



These striations are not the result of a momentary plica- 

 tion of the sub-cuticular membrane ; they depend on real pre- 

 formed organs, on transverse fibrils, situated in the sub-cuti- 

 cular layer ; for if, instead of placing the microscope so as 

 to observe the surface of the Gregarina, it is placed so as to 

 observe its optical section, one distinguishes very clearly on 

 the edges immediately under the cuticle refracting corpuscles 

 of circular shape, situated at equal distances from each other, 

 the diameter of which is just the same as that of the 

 transparent layer in which they are found (fig. "Z). Bv 

 changing progressively the ficus of the microscope, it is 

 seen that these corpuscles are only really optical sections of 

 the small transverse bands seen on the surface, and that 

 consequently these striations are produced by real transverse 

 circular fibrils. These fibrils, composed of a very refract- 

 ing substance, alternate with light clear striations, formed 

 by the fundamental substance of the muscular layer. The 



