624 Annals of the South African Museum. 



vesicle. The diagrams A to I in fig. 10, from drawings made at the 

 times stated, show the successive stages more fully than the incomplete 

 photographic record. 



The method of inversion is very like that found in the male globoid, 

 but the four lobes to the phialopore are far more distinct, and the whole 

 process more rapid. Judging from the inversion figures of daughter 

 colonies seen in V. gigas, inversion of the germ colony is even more 

 like inversion in the latter than in the sperm globoid, but living material 

 of that species has not as yet been examined (Pocock, p. 485). 



In another case observation started with the 2-celled stage half 

 an hour after noon. By 8 p.m. the 128-celled stage had been reached, 

 after which again observation was unfortunately interrupted by the 

 loss of the object in question. 



The need for speed in development is obvious. Except for its 

 power of movement in the earlier stages of development and the pos- 

 session of the delicate vesicle membrane, the zoospore and its product 

 are entirely unprotected and very liable to destruction. Of necessity 

 the cases quoted were under constant and very strong light, and it is 

 impossible to say what effect, if any, this would have on the rate of 

 division. It might quite conceivably exercise a retarding influence. 

 A series of experiments on the effect, if any, which light intensity 

 or continuity has on the development of the zoospore would be most 

 interesting. 



The difficulty of getting good accurate drawings is extreme, while 

 photography from the life is next to impossible to begin with, apart 

 from its small size the colour is so dark that, in addition to high 

 magnification, long exposure is necessary to obtain detail ; the earlier 

 stages are motile, and later the tiny object is rolled here and there by 

 the slightest current in the water or the movement of any of the 

 numerous motile unicellular plants or animals found with it in this 

 case, for instance, a very small and active chlamydomonas was most 

 trying. Finally, as soon as inversion is complete movement within 

 the vesicle begins. 



Appearance of the Young Colony after Inversion. 



On completion of inversion the young colony is somewhat reniform 

 in shape (Plate XLVII, G), soon becoming more or less spheroidal. 

 Immediately after inversion it measured 40 p. in diameter, 44 fj, before, 

 in a vesicle of diameter 55 /LI. 



Another, slightly older, measured 40 x 44 /n in a vesicle 58 x 60 p. 

 The cells are deep brown in colour and closely packed, and the cilia 



