EXTRAOVATE EXPERIMENTS. 



217 



is found at the spot where the extraovate is situated. From the fore- 

 going experiments it can safely be concluded that the deprivation of a 

 portion of cytoplasm as an extraovate induces the egg to manifest certain 

 disturbances in cleavage-pattern, and that the cleavage-pattern is already 

 established in the fertilized egg of Echinus? Arbacia and Strongy- 

 locentrotus. Furthermore it is interesting to note that the cleavage of 

 the egg of Strongylocentrotus is more affected by extraovate than 

 that of Arbacia. 



It is hardly necessary to add that an egg with an extraovate gives 

 rise to a perfect pluteus. 



Misaki Marine Biological Station. 

 July 19, 1910. 



Literature. 



DRIESCH, H., '93. — Entwicklungsmechanische Studien. III Uber 

 Variation der Mikromerenbildung (Wirkung von Verdünnung 

 des Meerwassers) : Mittheilungen aus der Zool. St. zu Neapel. 

 1 1. 



Driesch, H., '96. — Betrachtungen über die Organisation des Eies 



und ihre Genese : Arch. Entm. 4. 

 Jan.SSENS, F. A., '03. — Production artificielle de larve géante chez 



un échinide : CR. Jan. 27. 

 JANSSENS, F. A., '04. — Production artificielle des larves géantes et 



monstreuses dans Y Arbacia: La cellule 21. 

 LOEB, j., '94 a. — On some facts and principles of physiological 



morphology. IV The artificial production of double and multiple 



monstrosities in sea-urchin : Woods Holl Biol. Lec. for 1893. 

 LOEB, J., '94 b. — Uber eine einfache Methode, zwei oder mehr 



zusammenwachsene Embryonen aus einen Ei hervorzubringen : 



PFLÜGER'S Arch. 55. 



1) Drieschs result ('96). 



