Volvox in South Africa. 595 



complete continues uninterruptedly ; the globoid rotates on its axis, 

 which at the same time is constantly changing its direction, the 

 very characteristic peculiar compound motion resulting. 



Eventually the sperm globoid, which measures from 40 to 44 /JL in 

 equatorial diameter and about half as much in polar diameter, is 

 ready to escape. In general it escapes towards the outside, but a 

 small number may escape inwards into the hollow centre of the 

 mother colony, whence they may eventually escape whole through 

 some pore already present, but more usually they break up into their 

 constituent sperms within the body of the parent. Under normal 

 conditions such cases are, however, exceptional. 



As liberation approaches, the sperm globoid is seen to be moving 

 in the outer part of the vesicle, which begins to bulge outward, push- 

 ing apart the neighbouring vegetative cells ; the cilia bunch together 

 into this bulge, a small part of the wall becomes disintegrated, suggest- 

 ing strongly some form of enzyme action, and the sperm globoid 

 squeezes through, often showing considerable distortion as it does so, 

 but recovering immediately on reaching the outside. It reminds one 

 strongly of the distortion seen in an Oedogonium zoospore during 

 escape (Plate XLV, A, B). 



There is no tearing of the neighbouring cells as in the escape of the 

 larger daughter colonies, and after escape the cells fall back into 

 position so that the gap left is merely the space in the peripheral layer 

 originally occupied by the enlarged male initial cell. Further, the 

 inner part of the vesicle remains intact, and thus, even when the 

 majority of the sperm globoids have escaped, the parent colony is 

 not laid open to attack from outside and remains healthy and vigorous. 

 Since the escape of the several hundreds of globoids which such a 

 colony may contain is spread over a considerable period, probably 

 some days, this is an important consideration. 



In the case of a single large male colony under observation for 

 over an hour in the evening of 31st January 1931 the following 

 observations were made : 



Between 10 and 10.30 p.m. Six globoids were liberated out- 

 wards. 



10.50 p.m. One globoid escaped into the hollow of the parent. 



10.55 p.m. Watched a globoid escape at edge of colony outer 

 wall bulged slightly outwards, projecting part broke (or was 

 digested) and the globoid squeezed through sideways, being 

 considerably distorted in the process, but at once regained its 

 normal shape. 



