CLI-.\\ \(,I PLANE AND ENTRANCK POINT OF SPERM. 249 



di-turbance. In the sixty eggs counted the first cleavage furr\\ 

 passed through the sperm entrance-point in every case. In some 

 cases the indicator appeared to be at right angles to the furro\v 

 but in all such it proved to be aboic the egg and ended in the 

 cleavage plane (Fig. n). This was Sunday, August 20. The 

 laboratory was quiet, the temperature conditions favorable. 

 The results of Au.uu-i 23, 24 and 2~ an- Hinilar. I "amera sketches 



Fit;. 1 1. First i 



\\ t ! made of these eggs. Often I a-ked .111 in\ esl igator, who did 

 not know the purport of the experiments, t<> make the sketches; 

 the indicator without doubt was above the e.^ and pointed to 

 the elt-avagc furrow. 



DISCUSSION. 



Tin- first cleavage plane usually coinride- \\iih tin- median 

 plane of the future animal in the IV according to Koux, 



\e\\port, Pfliiger and Morgan. In the squid' I so, according 



it ' \\ .n.i-e, the first cleavage plane falls in with the median plane 

 of the embryo. Agassiz and Whitman (,'^41 nou-d a like co- 

 intideiH e in the teleost egg; and \"an Beneden and Julin, Castle 

 '96) and C'onklin ('05) found that the first cleavage plane marks 

 the Ion- axis of the embryo in the a-< -idian egg. 1 



:.liiiK to Harper, tin- -pt-rni .ntrr< tin- pixoin'- i-i;.c pn-vim< ti> tlic ogg's 

 riui.in.r into the oviduct. Il- In-li.-vc-; that th.- -pi-mi iiiu-t <-iuer as soon as the 

 ,li~r i~ i-\p, .-<-,! through rupture of the tollicular wall. In the p I..-MII 



i-ntiano- i- nu-ir ir I' ized. According to his figure, th( ige plane 



in.ik.- an .ui^l.- ..i 45 with the lonp axis of the embry> A- we know from oilier 

 j-ches, the Iniiv; axis "I the embryo is similarly placed in tlie egg. 



