March 27, 19(«.] 



SCIENCE. 



491 



2. As already recorded by Torrey, the 

 young Eenilla colony exhibits a strongly 

 marked polarity, a new axial polyp being 

 developed after removal of the anterior 

 end, a new peduncle after the removal of 

 the posterior end. After removal of the 

 peduncle posterior to the budding zone it 

 does not ordinarily regenerate a new axial 

 polyp. In a few cases, however, a normal 

 axial polyp was produced at the anterior 

 end of a severed peduncle, and in one case 

 this produced a symmetrical pair of buds 

 in the same position as the primary pair 

 of buds in the normal development. In a 

 single instance a reversal of polarity was 

 obtained, a severed axial polyp regenera- 

 ting a similar polyp from the basal end, 

 so that a two-headed monster was produced. 



3. After oblique section through the bud- 

 ding zone a process of remolding takes 

 place in such a manner as to cause one of 

 the lateral buds to occupy the position 

 formerly occupied by the axial polyp, while 

 the wound entirely heals. A new axis is 

 thus apparently established. At a later 

 period, however, this initial remolding is 

 overcome by a process of regeneration, a 

 new axial polyp developing at the point 

 corresponding to the position of the orig- 

 inal one, so that the lateral polyp is again 

 displaced to its original position at the side. 

 This indicates that the persons of the col- 

 ony are definitely specified and are not 

 interchangeable. 



The same result is given by operations 

 in which the peduncle is removed, together 

 with a single small lateral bud. In such 

 cases the remaining bud remains entirely 

 stationary in development, or may even 

 disappear, while a new axial polyp of full 

 size is regenerated from the cut surface. 

 In one case where the lateral bud remained, 

 a corresponding bud was formed on the 

 opposite side so as again to produce the 

 condition of the primitive colony with a 

 single pair of buds. 



4. These observations show that the in- 

 dividuality of the buds in Benilla has be- 

 come wholly subordinated to that of the 

 colony, which develops from the egg or 

 regenerates lost parts in essentially the 

 same way as an individual in the ordinary 

 sense. 



Notes on the Artificial Reversal of Asym- 

 metry in Alpheus: Edmund B. Wilson, 

 Columbia University. 

 As Przribram has described, the removal 

 of the large or hammer-chela in Alpheus 

 heterochelis causes the remaining small 

 chela to be transformed at the first or sec- 

 ond moult into a hammer-chela of the large 

 type, a chela of the small type being re- 

 generated in place of the large one that 

 has been removed. If after removal of 

 the hammer-chela the nerve of the small 

 chela be severed at the base, this trans- 

 formation does not take place or is incom- 

 plete. 



Comparison shows that the small chela 

 of the female conforms closely to the early 

 larval type, while that of the male is more 

 modified in a direction toward the type of 

 the hammer-chela. Since in the young 

 larva both chelse are alike (Brooks and 

 Herriek) and correspond in type to the 

 female small chela, the latter may be re- 

 garded as an embryonic type in a state of 

 arrested development, while the male small 

 chela represents a somewhat more advanced 

 state. In both cases the development of 

 the small chela is held in check by the 

 presence of the large one, the inequality 

 constituting an equilibrium characteristic 

 of the species. Removal of the large chela 

 releases the development of the small one, 

 and at the same time reverses the asjon- 

 metry of material. Regeneration then 

 proceeds along the same lines as in the 

 normal development until the adult equi- 

 librium is restored, but in a reversed con- 

 dition. In this case, therefore, an appa- 



