402 PROF. ALLMAN ON THE EECENT BESEAKCHES 



The protoplasm passes outwards throagli the neck, and expands 

 fungus-like oyer the margin, where it attaches the body to the 

 shell. From this fungus-like expansion the pseudopodia radiate 

 in all directions. 



The body consists of a pale bluish protoplasm with its anterior 

 half granular and its posterior half almost perfectly homogeneous. 

 In the posterior is imbedded the nucleus. This possesses the 

 form common to the nuclei of almost all the freshwater Ehizopoda 

 — that of a clear, perfectly colourless, spherical body containing 

 concentrically within it a spherical pale-bluish nucleolus. The 

 membranous investment which, in some Ehizopods, surrounds the 

 nucleus is here wanting. In the anterior granular portion of the 

 protoplasm lies the contractile vacuole. 



Hertwig and Lesser find the individuals not only united by their 

 pseudopodia into the loose colonies described by Archer (fig. 6, A), 

 but also, by a close union, constituting botrylliform clusters (B). 

 He regards these botrylliform clusters as identical with a form 

 described by Archer as an independent organism under the name 

 of CystopTirys Haecheliana, which is thus, according to Hertwig, 

 nothing more than a heap of Microgromia socialis. 



Hertwig has further found that M. socialis multiplies itself 

 by means of locomotive germs, a discovery of importance in 

 its bearing on the development-history of the Monothalamia. 

 He has seen the protoplasm of the various members of the 

 colony divide by a transverse constriction into two halves, 

 each with its nucleus and its contractile vacuole. The posterior 

 segment remains for some time free in the bottom of the shell 

 and then presses forward (C), and, by means of amoeboid move- 

 ments, escapes through the pseudopodial orifice (D). After its 

 escape from the shell the amoeboid movements continue, and the 

 germ now stretches itself out into the form of a worm, or con- 

 tracts into a globe, or forms a lobed mass of protoplasm spreading 

 over the pseudopodia of the mother colony. It then gathers 

 itself together, acquires an oval form, develops from one end a 

 pair of flagella, and forsakes the colony as a free-swimming swarm- 

 spore (E) ; or, in other cases, instead of becoming a flagellate 

 swarm-spore, assumes •AnActinophrys-Yike form and moves about by 

 the aid of three or four more or less branched pointed pseudopodia. 

 Hertwig was not able to trace them to their ultimate destiny ; but 

 there can be little doubt that both kinds of locomotive germs 

 come, after a time, to rest, excrete a shell, and lay the foundations 

 of new colonies. 



