Volvox in South Africa. 645 



FIG. 



C. Contents of globoid loosening, cilia nearly all drawn into vesicle, a few spermato- 



zoids nearly free (331). x 750. 



D. Globoid from which a number of sperms, some of which are seen free, have 



escaped ; many still moving inside. Fixed, iodine (201). x 750. 



E. Escape nearly complete ; a few sperms still active inside the wall of the globoid, 



which is now clearly visible. Above, part of a large mass of sperms escaped 

 from this and other globoids (308). x 750. 



F. Group of spermatozoids from globoid shown in D, with somatic cells (dark) 



torn from the parent colony. Fixed, iodine (200). x 1000. 



G. Free sperms. Killed, osmic acid (229). x 1000. 



PLATJ-: XLVI. 

 V '. Boussfhtii. The oospore and its germination. 



In A, F, 1, and .) vesicle wall, sperms and cilia slightly emphasised; 



photographs otherwise untouched. 



A. Mature oosphere with sperms swarming outside the vesicle wall (429). x 1000. 



B-D. Germination of oospore, first stage : escape from spiny exospore. x 500. 



B, two spores, the one on the right escaping from exospore (436). C, one 



spore free from the exospore, which lies empty on the left. In D, exospore 



is split, the spore-protoplast has enlarged (430). 



E. Spore after escape from exospore ; the protoplast, enclosed in the delicate 



endospore, lies eccentrically within the mesospore, which is stretching and 

 becoming thinner (437). x 970. 



F. Second stage: the spore on the right is similar to E, that on the left has en- 



larged considerably (431). x 500. 



G. H. Third stage: protrusion of endospore from mesospore, and passage into it 



of the protoplast. x 500. G, the spore has escaped from the exospore, 

 and a single zoospore is being formed, clear anterior end already well defined 

 (522). H, germination has continued within the split exospore; apparently 

 4 zoospores are being formed, but have not yet separated (436). 



I, 9.15 p.m. Zoospore recently escaped from endospore, cilia short, wall close to 

 protoplast, movement hardly begun (520). x 500. 



J, 9.55 p.m. Zoospore forty minutes later (killed, iodine), cilia lengthening, wall 

 enlarging (521). x 500. 



PLATE XLVIL 

 V '. Bousseletii. Development of germ colony from zoospore. 



A-F. Germ colony on completion of cell-division and its inversion. Living. 

 Ax 310; B-Fx410. 



A, 1.0 a.m. Cell-division complete, cilia of zoospore still attached to wall of vesicle 



(cilia and vesicle wall slightly emphasised) (502). 



B, 2.35 a.m. Inversion beginning, four lobes of phialopore opening (506). 



C, 2.45 a.m. Lobes beginning to turn back, phialopore wide open (507). 



D, 2.49 a.m. " Hat " stage (508). 



E, 3.0 a.m. Brim turning back over crown (510). 



F, 3.4 a.m. Inversion complete, cilia lengthening. 



G, Young germ colony recently inverted, rotating inside vesicle to which zoospore 



cilia are still attached. Fixed, iodine (434). x 970. 



