230 C, O. WHITMAN. 



the protoj)lnsm/' and thinks they arise independently of the tui- 

 cleus, although he does not deny that some sort of relation may 

 exist between their appearance and the destruction of the nucleus. 



Tol (TnrV)^ o" ^^^ other hand^ refers the origin of these two 

 radial systems to two centres of attraction which arise in two 

 opposite poles of the nucleus. 



Strashurger (^t^) als^o assumes two centres of attraction, 

 ■which he erroneously, as Biitschli has shown, supposed to be 

 the poles of the spindle. The reciprocal inlhience manifested 

 by nuclei, as well as the magnetic-like pictures presented by the 

 radial systems, favor the opinion that the poles of the amphi- 

 aster are centres of attraction. 



Brandt (-j-i-g- tW) maintains that these apj)earances are 

 called forth by amoeba-like pseudopodia of the nucleus itself. 



Villot ( 't '(.'') advances the same theory, and asserts that the 

 nucleus (" Protoblast ") receives its nourishment through these 

 pseudopodia, which actually drag into it masses of yolk which 

 are assimilated as in an amoeba. 



Schultz (thH^) attributes certain radial arrangements seen in 

 the egg of Torpedo, to a xnial property of the ))rotoplasm. 



These various opinions agree in this, — that there is a radial 

 phenomenon of the nucleus to be explained; but no one of 

 them, if we except, perhaps, that of Gotte and Biitschli, get 

 further than a statement of the problem to be solved. 



The discovery of these phenomena does not appear to be of so 

 modern a date as some authors have sujiposed who have 

 attributed it to Kowalevsky. The first, so far as I have 

 been able to ascertain, to mention such stellate figures, was 

 Derbes (|^) in 1847. He described each nucleus as a centre 

 d'nne radiation une pen confuse. Krohn (-g^'45 Ascidia, 1852) 

 described Irradialions centren around which the yolk was 

 arranged in radien/ormigen Streifen; llemak {\^) (Rana esculenta 

 1855) found radiate SIricfen in one of the upj)er cleavage- 

 spheres; Gigenbanr (54 Sagitta, 1857) ; Leuckait ('.jV > ^^*'""i" 

 toidea, 18G7— 187G) ; Kowalevsky (V%85,/„V. Ascidia, 18G6 ; 

 Euaxes and Lumbricus, 1871 ; Pyrosoma, 1875) ; Kupffer (-fl-j* 

 Ascidia, 1B70) ; Butschli (24, Nematoidea, 1873); Eol {^^, 

 Geryonia, 1873; Pteropod, 1875; Echinoderms, 1877); 

 Met'schnikoff {^\l, Geryonia, Polyxenia, 1874); Aucrbach (^'-/V 

 Neinatoidca, 1871); v;in Beneden {-\^, egg and blastoderm- 

 cells of rabbit, 1875), have seen and described more or less 

 fully the same phenomena. 



The Polar Figure. — It is impossible to say with certainly how 

 long before the o^'j^, is laid the archiamphiaster is formed. That 

 it is formed before d(j)osil is ])roved conclusively, not only by 

 sections of eggs taken iroiii llie ovary, but also by the examina- 



