259 
framework, able to act in virtue of its elasticity ; under the 
cuticle is found a layer of contractile substance, formed of 
muscular cells. 
We find also, in the Gregarine, this muscular layer. 
Leidy! was the first to recognise it, and he endeavoured to 
demonstrate that there exists under the cuticle a muscular 
membrane, which, when it contracts, becomes plicated lon- 
gitudinally, in such a way as to produce a well-marked stria- 
tion. lLeuckart? and Ray Lankester? have arrived at the 
same conclusion. In studying, by means of reagents, the 
immense Gregarine of the lobster, I have quite satisfied 
myself of the existence of a veritable system of muscular 
fibrille, comparable to the muscular fibrille of the Infusoria. 
I hope to be able to demonstrate the existence of this system 
of fibrille in a further work on the intimate structure of the 
Gregarina gigantea.‘ 
If we take into consideration only this single fact of the 
existence of a muscular layer, recognised since Leidy by all 
naturalists who have occupied themselves seriously with the 
Gregarine, we must recognise that these cells rise far above 
the Amcebe. In my opinion it is impossible to consider the 
Gregarine as Amebe which have undergone a retrogressive 
development. 
However that may be, the Gregarnie of the lobster passes 
successively, in the course of its embryonic development, 
through the following stages. 
1. Moner stage. 2. Generating cytod stage. 3. Pseudo- 
filarium stage. 4. Protoplaststage. 5. Encysted Gregarine 
stage. 6. Psorosperm stage. 
It is certain that few of the higher organisms even have 
so complex an evolution. 
Before finishing I have yet to examine the question as to 
whether one must admit a true alternation of generations in 
these beings. The solution of this question is entirely de- 
pendent on the question as to whether it is necessary to 
admit the existence of a true conjugation’ in these organisms. 
That certain species are always found attached end to end 
is incontestable. But we must not, therefore, conclude from 
1 Leidy, ‘ Transact. Amer. Phil. Soc. Philadelphia,’ 1852, vol. x. 
2 Leuckart, ‘Jahresbericht Archiv fur Naturgesch.,’ vol. xxi, p. 108. 
3 Ray Lankester, ‘ Quart. Journ. of Micros. Science,’ 1863. 
4 Ina more recent work, Ray Lankester expresses the opinion that the 
longitudinal striation depends on the cortical protoplasmic layer.—Notes on 
Gregarine, Ibidem, 1865. 
5 By true conjugation, I understand a fusion having for its object 
fecunda tion. 
