120 W. ARCHER. 



contained three segments (each with nucleus and contractile 

 vacuole) — one large and two small — their pseudopodial 

 stems in mutual connection ; hence they must have arisen 

 by a longitudinal fission of the original body-mass. In 

 several instances the author was able to follow the exit of 

 the two smaller individualised portions, one after the other. 

 For more than an hour the young individuals each crept 

 along a pseudopodium like little Amoebae, without showing 

 any inclination to become modified into zoospores or to 

 leave the colony. The author was unable to carry this ob- 

 servation any further. 



Although an encysted state must doubtless take place 

 during the dry periods of the year, the author did not see 

 any indication of it. 



So far as its simple development-history is disclosed by 

 the foregoing observations, there is nowhere any indications 

 of any sexual process. At no point was there any diff'erence 

 in the nucleus observable. The only process observed and 

 described was simple self-division, but the mode of origin 

 of the two nuclei, whether by division or fresh formation, 

 remained to the author in abeyance. 



Cienkowski carried out some observations on a form re- 

 ferred by him hereto, and I believe it must be identical with 

 this (although I doubt if Microgromia ever shows the pseu- 

 dopodia so extremely finely linear and filamentary, and so 

 seemingly homogeneous and granuleless, as he depicts in his 

 figure); he noticed many cases of self-division, mostly longi- 

 tudinal, but likewise often transverse, and in both cases the 

 one segment emerged from the test as a zoospore, so that he 

 seems rightly to place no value on the circumstance of the 

 fission being longitudinal or transverse. As regards the 

 act of self-division it was always preceded by the appearance 

 of a second nucleus, which he states to originate indepen- 

 dently, and not by the division of the " mother nucleus \" 

 the plane of subdivision of the body may be oblique or longitu- 

 dinal. As to the mode of exit, movement and general structure 

 of the zoospore, the author's account agrees with Hertwig's, 

 but he avers that it is a matter of indifference, which seg- 

 ment — the upper pseudopodial-stem-bearing, or the under 

 simply rounded one — may emerge to become the zoospore. 

 He was unable to make out anything definite as to the 

 mode of origin of the colonies, though such seemed to be 

 more abundant in the summer months. (My own opinion is 

 the autumn, often late, is the season in which the Rhizopoda 

 of the freshwaters are most readily to be met with.) 



The formation of zoospores thus seems to be bound up with 



