284 PKOF. ALLMAN ON THE RECENT EESEABCHES 



referable to the contraction of the protoplasmic network. It it; 

 here comparable to the well-known granule-currents in sarcode 

 filaments. One can hardly help believing, however, that the real 

 nature of the filamentary network in Labyrinthulea has been 

 misunderstood by Cienkowski, and that in this, as well as in 

 Clilamidomycois, it constitutes a true protoplasm-net. 



The long-known " sun animalcule," Actinoplirys sol, has recently 

 been studied by Hertwig and Lesser *. These excellent observers 

 have especially attended to that part of its structure which was 

 maintained by Grrenacher to correspond to the central capsule of 

 the Eadiolaria, and have shown it to be a large nucleus with nu- 

 cleolus, as, indeed, Stein had already maintained to be the true 

 import of this body in A. oculata, a closely allied marine form. 



The researches of Hertwig and Lesser have now left no un- 

 certainty regarding the structure of this most interesting little 

 Rhizopod, so that a definition more exact than any hitherto 

 attempted can be given of it. The true conception of A. sol 

 would be thus, according to these observers, that of a spherical 

 Ehizopod with the protoplasm forming its central part homogene- 

 ous and that of its peripheral part vesicular. In its peripheral por- 

 tion is a single contractile vacuole, which projects far beyond the 

 surface. In the centre of the body is the nucleus with a distinct 

 membrane and large nucleolus. The pseudopodia, which radiate 

 in all directions from the surface, are provided with an axis- 

 filament ; 'they are loaded with granules, seldom anastomose, and 

 never branch. 



The union of numerous individuals of A. sol into a single mass 

 has often been observed. The number thus fused together is 

 variable and has been estimated at from two to nine ; and the 

 fusion is so intimate that it is impossible to demonstrate the 

 boundaries of the component individuals, the compound mass 

 appearing as a single Actinophrys. The nuclei, however, remain 

 distinct, and give evidence of the composition. The tendency to 

 combine shows itself also m the pseudopodia, which, in the com- 

 pound masses, exhibit numerous anastomoses with one another. 



The individuals which have thus become amalgamated may sepa- 

 rate from one another and then become once more united into a 

 common mass. 



It is not at all likely that this phenomenon of conjugation has any 

 thing to do with a trul)' sexual differentiation ; nor can ^Ye, indeed, 



* Loc. cit. 



