1899] REGENERATION 319 



no " Anlagen " be necessary to the occurrence of regeneration, there 

 are none to disappear when regeneration becomes useless on account of 

 the unimportance of an organ. It is true that Morgan does not state 

 that this conclusion is reliable, and it will need a much larger number 

 of experiments to prove it satisfactorily. A continuation of these 

 experiments might also yield much in other directions. It would be 

 necessary to observe the complete development of the regenerated 

 abdominal appendages in order to be able to say definitely whether 

 they were reproduced in the same form, or whether here too there was 

 reversion to an older type. If the above conclusion be correct, i.e. if 

 the phyletic variation of the regeneration-" Anlage " goes on more 

 slowly than that of the transforming organ itself, we should expect, for 

 instance, that in the regeneration of the last abdominal appendage, the 

 present form — which serves as a holdfast — would be renewed after the 

 pattern of the tail-fin of the Macrura. This is, of course, only a 

 supposition, and it is perhaps more probable that in this case the 

 regeneration-" Anlage " has followed more closely on the transformation 

 of the organ, as it must be of importance that the holdfast should be 

 renewed as such. Of course this argument would fall to the ground if 

 it were shown that injury to this sixth abdominal appendage hardly 

 ever takes place ; for then there would be no reason for the progressive 

 modification of the regeneration-" Anlage." But the statistics given 

 are not nearly comprehensive enough to admit of any certain conclu- 

 sions being drawn from them, and further experiments are much to be 

 desired. 



Let us now discuss another experiment made on frog-tadpoles, 

 which, if it be corroborated, will be of fundamental importance to the 

 question of regeneration. Before the first external indications of the 

 hind-legs appeared, Esther Brynes x destroyed the whole region of the 

 body-wall from which the legs grow with a hot needle, and observed 

 that perfectly normal limbs were nevertheless formed. The experi- 

 ments of Barfurth had previously shown that the legs of young tadpoles 

 become regenerated, and had also established the fact, which seems to 

 me very important, that this power of regeneration is rapidly lost as 

 the tadpole grows. These experiments are quite in accordance with 

 the theory of the localisation of the regeneration-" Anlage " at the base 

 of the leg, since it must somehow be present at this stage. Esther 

 Brynes's new experiment, on the other hand, tends to show that at 

 an earlier stage there is also regeneration of the leg without any 

 localised " Anlage," and that at this stao-e the limitation of the 

 " Anlagen " to the cells of the mesoderm has not yet taken place. 



The knowledge we have already acquired through the numerous 

 and variously modified experiments with the blastomeres of the 

 developing ovum here receives a new and very precise corroboration. 



1 On the regeneration of limbs in frogs after the extirpation of limb-rudiments," Anat. 

 Anzeig. 1898, Bd. xv. No. 7. 



