212 EDWARD VAN BEXEDEN. 



The cell has only now to grow to become the beautiful 

 Gregarine, of the ri-roth part of a metre long, to which 

 the lobster complaisantly gives home and nourishment ; but 

 at the time of its growth the cell undergoes in its proto- 

 plasmic body new phenomena of diifercTitiation, and the 

 complication which then appears in the cell-body allows one 

 to affirm that certain monocelkilar organisms can present a 

 real organization, and that they are composed of parts which 

 must be distinguished, as mvich from a morphological point 

 of view as from a physiological one. Before describing this 

 complication of structure, and in particular those elements 

 that constitute inside a monocellular being a real muscular 

 system, I have thought it necessary to recall, in a few words, 

 the results of my investigations on the evolution of the Gre- 

 garinse, because they show that the Gregarina is but one 

 single cell, and that it represents to us, without any doubt, a 

 monocellular individuality. 



The giant Gregarina's body is of a cylindroid shape ; its 

 diameter varies little, at the most a small progressive nar- 

 rowing in its terminal parts, and a slight dilatation, the deve- 

 lopment of Avhich is variable, near its anterior extremity. 

 A cellular membrane, which I call cuticle by analogy with 

 with the cuticle of Infusoria, limits the body externally, and 

 the Gregarina is really only a long cylindrical sac, closed at 

 each of its ends. This membrane shows no trace of mouth 

 nor orifice, nor are any canalicular pores distinguishable ; 

 it appears perfectly homogeneous, and the nutritive liquids 

 can only penetrate by endosmosis. The membrane is of 

 the same thickness in every part. In individuals which 

 have reached their complete development its limit is most 

 exactly fixed on the inside as well as on the outside, and 

 shows a strongly marked double contour. But this is not 

 the same in young individuals ; in them the cuticle is very 

 difficult to find, because it is not completely isolated from 

 the subjacent protoplasmic matter ; there is an imperceptible 

 passage between the contents of the cell and the external 

 coating of the protoplasm, which gradually transforms itself 

 into a cortical substance. 



The contents of the cell, forming the parenchyma of the 



psorosperms of hif^her animals confirm on all points my investigations on 

 ihe evolution of Hie Gregarinae of the lobster. The phases of psoro- 

 sperms (figs. 53, 54, 56, and following in his work), of semilunar 

 bodies, swelling at one end (fig. 34), of scythe-shaped bodies (fig. 3G, and 

 following), of semi-ovoid cells (fig. 47), and of nucleated Gregarina, corre- 

 spond to the conditions which I have designated under the name of 

 Monerian condition, of generative cytod, of pseudo-filarium, of young 

 Gregarinae, and of complete Gregarinas. 



