SCIENCE 



[S. S. Vol XXVIII. Xo. 713 



This point I have been aWe to determine by 

 means of the " attachment funnel " (,mioio- 

 pyleO of the ess>mei«bRuie. Boveri has 

 shown that the funnel oorr^spouds to the point 

 of attachment of the eg^ to the wall of the 

 ovivry. It lies opposite to the point of forma- 

 tion of the micromeies in the normal egg, 

 and therefore also opposite to the gastrula pole 

 of the eg^. I find that in the centrifuged 

 egg of J.r?Hu-k» the mioiomeres also appear 

 opposite (.or as nearly so as possible) to the 

 attachment funnel, without regard to the 

 stratification of the materials- 



iliss G. R Spooner. working with me, has 

 demonstrated that wherever the miciomexes 

 lie on the centrifiigevl egg there also the 

 gastrulation takes place. Putting together 

 these facts, it is evident that the axis of the 

 «nbryo derivevl from the centrifuged egg is 

 the same axis as that of the normal egg. In 

 other words, the location of the nucleus, of the 

 oily matter, of the yolk, and of the pigment 

 of the egg has no determinative influence on 

 the location of the eaubryonic organs. These 

 visible materials are not organ-forming, nor 

 do they act as initiators of organ formation. 

 Even retuoval of the nticlens from its normal 

 relations to the egg^axis has no balefttl in- 

 fluence on the development. 



The results demonstrate that the location of 

 eanhryo-fonuing regions is a cytoplasmic and 

 not a nuclear phenomenon. Bovijri's classical 

 e:speriment with dispermic ^s*- which he 

 brought forward in order to demonstrate the 

 importance of the nucleus in the early de- 

 velopment, receives an entirely different in- 

 terpretation in the light of these facts. The 

 conclusive demonstration of the location of 

 the primary axis fumishevl by the experiment 

 given aK^ve leads to some far-reaching con- 

 chisions concerning the factors of devielop- 

 ment, and the supposed value of the gpceser 

 materials of the egg as organ-forming sub- 

 stances-: 



1. By means of the centriftxge it is possible 

 to drive the nucleus, the yolk, and pigment 

 granules throtigh einbTvo-forming materials of 

 the egg without necessarily affecting the polar 

 rdations of th^-^e materials, and without neces- 



sarily iiyuring them for fxirther development. 



2. The displaced nucleus does not return 

 to its original position before cleavage, and 

 its new location determines the position of the 

 first plane of cleavage. There is no essential 

 relation between this plane of division and 

 the planes of the embryo. 



o. The embryonic axis is determined in the 

 egg. but whether it is the outcome of an 

 arrangement or gradation of materials which 

 are not affected by the eentrifuging. or 

 whether it is due to a hidden structural basis 

 ('• organiration ") can not perhav>s be deter- 

 mined from the evidence. When all the facts 

 are taken into consideration, however, the 

 former alternative seems to be more in accord 

 with the results. 



4. After eentrifuging and before cleavage 

 there is to some extent a remixing of the 

 separated substjvnces, but this partial return 

 shows no evidence of redistribution in the 

 direction of stibsequent organ-formation, but 

 is due to movements connected with karyo- 

 kinesis. 



5. The possibility that formative substances 

 are present other than the visible substances 

 her«« referred to must, of conrse. be admitted, 

 but stich materials ar^ in the egg of the sea- 

 urohin not seriously disturbed by a centrifugal 

 force sufficient to ss?parate the visible sub- 

 stances of the ^s- Chi the other hand. I 

 have found for the egg of the f rv^g that a speed 

 higher than that necessary to separate the 

 grosser materials interferes with the normal 

 development, and in such cases it seems not 

 imprv^bable that more fundameatal materials 

 becv>me displaced. 



d. The experiments do not show con- 

 olttsively the origin of the bilaterality of the 

 embryo, but they do show that this is not 

 caused by the stratification, nor ry anti par- 

 HcvJiir cifdvcigf platif. xlox by the position of 

 the nucleus.' The inference that bilaterality 

 is also " given " in the egg- seems therefore 

 most plausible. T. H. Mokgas 



Wooi»s Hoii. 

 Axjgust 17. 190S 



'- The evidence cai which this statement rests is 

 only partly given iu the present ec«nmum<atioa. 



