EMBRYOLOGY OF CLEPSINE. 255 



dem Auseinanderweichen vollstandig von elastischen Hiillen 

 uingeben seien, und dass die letzteren, indem die Kugeln, 

 wahrscheinlich in Folge der Sckwere {!), mit ihren Randpartieen 

 sich allmalig trennen und abrunden, durch die uugleichmassige 

 and schwierig erfolgende Losung der Adluirenz ungleichinassig 

 angespannt und zur Faltenbildung veranlasst werden (yirf)- 



2. Max Schultze (VV) maintains that cleavage results from 

 contractions of the yolk, and that these contractions create in 

 the viscid cortical layer of the vitellin the so-called " folds." 

 " Quum vero vitelli substantia imprimis corticalis glutinosam 

 quandatn et viscosam praebeat coasistentiam, non mirum videri 

 protest, eodem tempore quo sulcus contractilitate vitelli paullatira 

 exoriatur, incisuras apparere minores, pHcas seu rugas sulco 

 vicinas et recto angulo in sulcum vergentes/' 



3. Gotte (^^) interprets them as a mere " Ausdruck fiir die 

 Ausgleichung an der Oberllache des dickfliissigen Dotters 

 . . . . gleichwie etwa bei einera Stich in eine teigige 

 Masse, oder bei einer Einschniirung derselben, Falten enstehen." 



Three facts seem to be irreconcilable with the above inter- 

 pretations. 



1. These *' Falten " appear only on one pole of the egg. 



2. They are at right angles to the cleavage-groove only in 

 the centre, diverging more and more towards either end of the 

 same. In consequence of this divergence a radial system is 

 formed, or as Reichert (^^It) expresses it, a long star. 



3. The lively play (" lebhaftes Spiel," Gotte) of tbese 

 "Palten."' 



According to the explanations of Reichert, Schultze and 

 Gotte, the ^'Falten" should accompany the cleavage-furrow 

 entirely around the egg, and should run at right angles to the 

 plane of division. This, however, is not the case. To what 

 class of phenomena then do they belong? Are they not to be 

 classed with those now well-known radial arrangements of the 

 yolk during cleavage, and consequently to be referred to nuclear 

 influence. Their appearance on one side of the egg, their 

 radial arrangement, and their behaviour, all seem to suggest this 

 interpretation. The pseudopodes of the Hydra-egg can be 

 interpreted in the same way. I have already pointed out the 

 fact that the amphiastral radiations-reach their maximum intensity 

 at the time the cleavage begins. It is at this time that the 

 " pseudopodes " appear in the egg of Hydra, and the " Falten " 

 in the ovum of the frog. Furthermore, my sections show that 

 the first cleavage-amphiaster lies nearer the oral than the aboral 

 pole, and it is on this account that the cleavage-depression 

 begins sooner on the upper than on the lower pole. The same 

 is probably true in all cases where this mauner of cleavage 



