400 CHIKANOSUKE OGAWA 



before complete development of the lens, the exact time necessary 

 for the whole process cannot be given here, In general, after the 

 development of the lens attains a certain stage, further change 

 is slow. 



In order to confirm the possibility of regeneration in winter, ten 

 animals were operated upon the middle of December, and the 

 eyes were examined after forty days, but no indication of re- 

 generation, such as depigmentaion and thickening of the iris 

 epithelium, could not be found at all. In this case the tempera- 

 ture of the aquarium, where the animals were kept, ranged from 

 7° to 4°C. Difference in duration of regeneration according to 

 the season and absolute lack of regeneration in winter seem most 

 likely to depend upon temperature, though food might play 

 some part. 



Individual difference in time of regeneration is fairly marked, 

 even if the animals are kept under the same conditions; twenty 

 specimens were studied three weeks after operation, and the re- 

 sults showed that the regenerated lenses are variable in size, the 

 largest being several times larger than the smallest. 



EXPERIMENTS ON THE IRIS 

 Lack of regeneration from the lower iris 



In regeneration of the lens from the upper iris, depigmentation 

 occurs also in the lower iris. Fischel considers this change as par- 

 ticipation of the lower iris in the first stage of regeneration. But 

 true regeneration never takes place from the lower iris. Fischel 

 ('00, '03) demonstrated one such case and maintained his inter- 

 pretation against Wolff's objection, but his case is not without 

 doubt, because the small lentoid, which is in connection with the 

 lower iris and also in contact with the larger regularly formed lens, 

 might have arisen from the latter and only secondarily come into 

 connection with the lower iris edge. 



Now the question naturally arises whether regeneration may 

 occur from the lower iris, if it is prevented from occurring from 

 the upper iris. I'or this study, total synechia of the upper iris 

 was brought about in the following way. The cornea was cut 

 horizontally in the upper part. After removal of the lens through 



