33 



aspects of one and the same dividing alga were observed : Fig. 

 29 a — d. In a the alga is seen exactly at the least bent part of 

 the wall (= h seen from aside); in h the alga is seen on the top 

 (= a on top); in c in a position between a and h] and in d more or 

 less from below ( = a in slanting upward direction). This alga 

 with its surrounding amoebocyte has been observed for 1^ hour. 



It is a matter of course that I observed a great many of those 

 stages of division, much more than have been drawn here; they 

 were all like these; I will only add Fig. 31. 



Besides these double-stages, there also occur plural-stages of 

 division, but much less numerous (Fig. 32—34). 



What I have mentioned here about the cell-division for the 

 chlorophyll corpuscles of Spongilla concerns also the symbiotic 

 algae of Ephydatia as well as the similar algae, which occur 

 free in nature. 



As I stated above, free in nature these algae often occur 

 sticking together in groups of 10 — 120 specimina, sometimes sub- 

 dived in small groups of 4 specimina. Evidently we have to do 

 then with the result of 2 successive divisions of a single cell. 

 Moreover, one may sometimes find the algae of one group (of 

 10 — 120) in almost the same stage of development; so, probably, 

 all of them originating in one cell. Neither the smaller groups 

 of 4, nor the groups of 10 — 120 pieces are ever to be found 

 surrounded by a common membrane or wall. Nevertheless, the 

 (round) corpuscles often obstinately stick together, when we try 

 to separate them; so, apparently, they are kept together with 

 a kind of slimy substance. 



So we have stated^ that the green symbiotic alga of the Spon- 

 gilUdae midtiplies hy simple^ vegetative division of the whole 

 mother-cell {into two), the new separating ivall sticking to the 

 mother-wall and, consequently, also dividing the latter (into two). 

 So there exists here no cell-division within, and independent of 

 the mother-cell-tvall, therefore no „freie Zellbildimg'" . 



Thus the symbiotic alga does not at all answer the definition 

 given by Beijerinck for Chlorella; neither the definition given 

 for Chlorella in modern literature — Grinzesco (24) 1903; Olt- 



