RECENT MEMOIRS ON FRESHWATER RHIZOPODA. 119 



colony ; by their slow action the segmented portion became 

 pushed along^ dragging after it the pointed hinder vacuole- 

 contalning end. The author was able to follow one of 

 these till it came to rest. Becoming ovate, it noAv developed 

 at the hitherto posterior end a pointed protoplasm-process ; 

 inasmuch as this agreed in relative position, as regards 

 nucleus and contractile vacuole, the author was inclined to 

 regard it as the commencement of the pseudopodial stem, 

 but, even after two days' observations of the individual, he 

 could not follow out the formation of the test, manifestly a 

 very slow process. 



The substitution of the actinophryan germs for the flagel- 

 late zoospores, when, by the light of modern observations, 

 we consider the relation of flagella to pseudopodia, is not in 

 reality very surprising. In the zoospores of Microgromia 

 itself the author had satisfied himself that at first the flagella 

 were temporarily projected and completely retracted only to 

 be reproduced at a new place. 



Touching the further question of the growth of the colony, 

 the author was unable to see how from a single individual 

 so originating a second individual becomes developed in con- 

 nection with it, though doubtless it is by a similar process 

 of self-division. In the course of the author's observations 

 during the summer, he frequently found " Cystophrys " 

 colonies in which in the greater number of the individuals 

 the body was divided into two ; the two segments, however, 

 side by side, each with its nucleus and contractile vacuole. 

 In these cases he never had an opportunity to follow the sub- 

 division from beginning to end so as to decide whether the 

 fission took place transversely or longitudinally. From the 

 fact, however, that he noticed so many cases in which the 

 pseudopodial stem was subdivided and the connection of both 

 portions with the colony seemed still maintained, he con- 

 cluded that the fission was longitudinal. He was, however, 

 able sometimes to see one of these portions slowly make its 

 exit from the test, leaving the other behind ; the contractile 

 vacuole in front, the nucleus hindermost. But unlike the 

 zoospores, no amoeboid action ensued, the mass remaining 

 globular, near the mouth of the test, and in union with the 

 remaining portion by a broad protoplasmic process (pseudo- 

 podial stem) ; by degrees it assumes the characteristic bilateral 

 symmetry (before described). As regards the formation of 

 the test the author has nothing certain to record. 



The author mentions, finally, yet a third modification of 

 this mode of development. In certain colonies, so under- 

 going subdivision, he noticed several individuals whose test 



