BUDDING TENTACLES OF GONIONEMUS. 249 



not warranted. They found dividing cells in the entoderm as 

 well as in the ectoderm, a condition which Lang did not find. 

 They found no trace of ectoderm cells migrating into the ento- 

 derm even in the earliest stages, of the two layers running into 

 each other, of the entoderm being pushed aside and absorbed. 

 Many others also have questioned Lang's claims and maintain 

 that results obtained in many species of hydroids, as well as in 

 other forms of animal life, confirm the old view. My own work 

 on hydroids l confirm these results of Seeliger, Braem and others. 

 In working on the regeneration of Tnbnlaria crocca, T. tcnella, 

 T. larynx, Eudendrium rainosnin and Pcnnaria tiarclla particular 

 attention was paid to structures which form either wholly or in 

 part by budding. Sections made through these buds in all stages 

 showed none of the features claimed by Lang, such as migrating 

 entoderm cells, dissolution of the supporting layer with the ac- 

 companying disappearance of sharp contrast between the two 

 layers, and absorption of the entoderm. Often, usually indeed, 

 the entoderm seemed to be the layer most active in this process. 

 Mitotic division was observed in both ectoderm and entoderm 

 though not abundant, reasons for which are discussed in the 

 above-mentioned paper. Amitotic division was also more or less 

 prevalent in both layers. Perkins (op. cit., p. 784) referring to 

 the formation of the tentacle in Gonioncunts says the three 

 layers, ectoderm, entoderm and supporting layer " are pushed 

 out somewhat in the growth of the tentacle, the region of greatest 

 activity being the endodermal layer, where the core of the tentacle 

 is formed by a rapid outgrowth of the cells of the body wall ac- 

 companied by multiplication of these same cells." He further 

 states that there is not even an initial thickening of the ectoderm in 

 the region where the tentacle is to appear. In regard to budding 

 in the larval form likewise, he states that the ectoderm and ento- 

 derm cells divide, the entoderm pushes out gradually, the ecto- 

 derm growing so regularly as to cover it with a layer of constant 

 thickness. Thus it has been conclusively proved that budding 

 in many hydroids, as well as in the formation of the tentacle and 

 in other buds of Gonioiicimis, involves both layers, and cells in 

 both layers increase rapidly by division. This would entirely dis- 



^ Arch. f. Ent-mech., Bd., XVII., Heft I, 1903, pp. 64-91. 



