12 



Miss D. J. Lloyd. Influence of Osmotic 



The decrease in rate of regeneration can be measured proportionately by a 

 consideration of the time taken to reach some definite stage. Two such 

 points are considered here : (1) the time taken for the healing of the wound ; 

 (2) the time taken for the perforation of the new mouth. These figures are 

 summed up in Table II on p. 11. 



It can be seen that regeneration is most rapid in solution 9. This solution 

 consists of 100 c.c. distilled water + 500 c.c. sea-water. Eegeneration in this 

 solution is accompanied by reduction (absorption of the yolk-glands, etc.), 

 but the regenerative processes proceed very rapidly, and, at the moment when 

 the normal form is restored, reduction has not gone so far as to have removed 

 the whole of the genital system. Under these conditions the secondary 

 sexual apparatus is redeveloped in the new tail. This also occurs in 

 solution 8 (100 c.c. distilled water + 200 c.c. sea-water). In more hypotonic 

 solutions, in sea-water and in hypertonic solutions, restoration of the normal 

 form is a much slower process. In these solutions, the reduction due to 

 regeneration + the reduction due to the longer starvation, make it impossible 

 for the worm to redevelop the secondary sexual organs, even after the normal 

 form has been restored. 



In normal sea-water or hypertonic water, the removal of the posterior end 

 of the worm acts as a check on the production of sperm. Sperm present in 

 the testicles at the time of section remains there, and, though the activity of 

 the sperrnatocj'te cells does not immediately cease, it is greatly diminished, 

 and, as regeneration proceeds (under starvation conditions), the whole 

 generative system is slowly absorbed to feed the growing parts. In worms 

 regenerating in hypotonic water, the production of sperm continues for some 

 time longer, and the sperm produced leaves the testes, passes down to the cut 

 end of the vas deferens, where, being unable to escape, it collects in sinuses, 

 one on either side. This condition is shown in fig. 10. 



In figs. 11 and 12, A and B, are shown camera drawings of gut cells {g.c.) of 

 animals regenerating in hypo- and hypertonic water, and also, for comparison 

 gut cells of normal whole animals. In the strongly hypotonic solutions the 

 cells are swollen and vacuolated, and the cell boundaries are hard to 

 distinguish. In the hypertonic solution the cells are shrunken. This fact 

 suggests that in the one case water has actually been absorbed by the 

 tissues, and in the other case extracted from them. From this it appears 

 that the epidermis in Guncla must be a highly protective membrane, since 

 whole animals placed in similar media show no such changes. 



A histological study of the tailless forms produced at 33'5 atmospheres was 

 made by sectioning the worms at various stages. These sections show certain 

 peculiarities in the behaviour of the parenchyma cells. In sea-water after 



