180 The American Naturalist. [Februuy, 



days divided into two almost separated spheres each of wind) became 

 a gastrula and finally a platens attached by a narrow isthmus to its 

 fellow. 



This abnormal action of the embryo is not confined to a simple 

 two-fold division : in three cases the blastula dividtd into a j and a 

 t section of which the former became plutei and the latter, in one case 

 a gastrula. The general distribution of this power to produce com- 

 plete individuals was more striking in a case where \ of a shaken egg, 

 in the two celled stage, died and the remaining ] of the egg became 

 a normal blastula ! 



Attempts made by the author to separate the blastomeres of Frogs 

 and of Planorbis have as yet been unsuccessful. There seems need of 

 extension of this experimental work before any wide-reaching con- 

 clusions can be drawn. 



Regeneration of Lost Parts. 1 — In these two papers the author 

 has given an important addition to our knowledge of the process of 

 regeneration of the tail in Batrachia. Both adult and larval urodeles 

 and larval anurans were used, though most of the work refers to 

 Rana and to Siredon larva?. In the first paper the interesting fact is 



case may be. Yet they become later like the original tails. This 

 change the author assigns to the eili-.-t oi'u.-e, to functional adaptation. 

 This is made probable by a number of experiments in which larvae 



tail. Some of the final straightening in tin non-swimmers is referred 

 to the effect of gravitation, but there still remain eases in which only 

 the " directive power " of the otgan ism seems to be concerned in the 

 ultimate return of the new tail to its proper use. 



The great length of the second paper forbids its proper treatment 

 in the present notice, its chief advance over previous work, of which 

 it furnishes a good confirmation, lies in the discovery of the fact I hat 

 the histological changes concerned in the formation of the new tail 



the spinal cord, chorda, connective ti-sue, cutis, blood-ves.-els striated 

 muscles and peripheral nerves in the order irjvom Simple tissues arc 

 quickly regenerated, the more specialized, more slowlv. Moreover, 



