412 E. I. WERBER 



'97) on the eggs of Triton cristatus. These interesting results 

 were subsequently supplemented by the important experiments 

 of Spemann ('00-04) who produced various duplicities in Triton 

 taeniatus by incomplete constriction of the eggs along the first 

 cleavage plane or along the corresponding plane at any stage 

 up to the gastrula. 



Bearing in mind these data as well as also Morgan's much 

 earlier ('93) discovery of the totipotency of the blastomeres 

 after the first cleavage in the teleost egg (Fundulus) it would 

 seem perfectly safe to assume that the duplicities recorded in 

 our experimeuts (on the eggs of the same species) have resulted 

 from (primarily osmotic) dissociation ('blastotomy' — Bataillon, 



I.e.)- 8 



The origin of the double embryonic anlage can, in this way, 

 be accounted for without difficulty — at least in anamniotes. 

 So far as this point alone is concerned it would seem no longer 

 necessary to resort to such assumptions as ' dichotomous growth' 

 at the anterior end of the embryonic anlage (Gerlach, '82), 

 or the oft-assumed binucleate eggs and coincidental polyspermy 

 as the agent causing duplication, or the 'radiation'-theory 

 of Rauber ('79-80) and its modified offshoot, the 'double gas- 

 trulation'-theory of 0. Hertwig ('92, '06). 



The inadequacies of all these hypotheses have been clearly 

 pointed out by Fischel ('02) and in full agreement with the lat- 

 ter also by Schwalbe ('07). To Fischel we also owe what may 

 be regarded as the most rational analysis of the manner in which 

 the various combinations of duplicities in teleosts may be formed. 



Fischel's considerations are based primarily on the assump- 

 tion of a duplication of the germinal anlage soon after fertiliza- 

 tion probably by abnormal osmotic pressure, as demonstrated 

 by Bataillon (I.e.). Starting thus with two embryonic primordia 

 and bearing in mind the mode of formation of the embryo as 

 established (particularly for the teleosts) by several authors 

 and notably by Kopsch ('96) Fischel, by employing the dia- 



8 This assumption might reasonably be extended to the double embryos often 

 recorded in fish hatcheries (notably in Salmonidae), where an abnormal osmotic 

 pressure may be due to temporary impurities of the water. 



