222 PEOCEEMNGS OF THE MAIACOLOGICAL SOCIETY. 



1891, in the assertion by Pol tLat in the sea-urchin {Strongylocentroius 

 lividus) he had observed a complicated metamorphosis, to which he 

 gave the name ^^ quadrille des centres''''^ and attributed paramount 

 significance in heredity. Fol did not long survive this, but more 

 recently a French Botanist, Gui guard, professes to have observed a 

 similar metamor[)hosis - in the lily, wherefore it might appear to be 

 of prime importance in organic development. 



Attention unprecedented has this ' attraction sphere ' received 

 within the last five years. It always lies in the focal point of 

 radiations of the cell protoplasm, and it has accordingly appeared to some 

 that it marks a centre of attraction of a convergent, and to others 

 of origination of a radiate, activity. With extending inquiry, how- 

 ever, Fol's and Guignard's assertions have been found erroneous,^ and 

 a growing suspicion has arisen that the centrosome is no organ 

 of the cell, but merely a condensation point, indicative of the passage 

 of some energy within the cell, of the nature of which we know 

 nothing.^ Concerning the astrosphere, Morgan has lately shown, ^ 

 by experiment on the egg of certain Echini and Tunicates, that under 

 treatment with 1"5 per cent, salt solution, vital activities are set 

 up within the egg which result in the appearance ad hoc of 

 ' astrospheres ' that closely resemble those of normal divisional 

 activity, and may be induced during periods at which, according 

 to prevailing deduction, their appearance ouglit to be impossible. 



In view of this, it may be asked whether with the egg, as with 

 the adult organism, we are not in error in generalizing upon this or 

 tliat part considered alone. The entire form and habitus of both 

 animal and cell are the expression of co-ordinate activity between 

 its different parts, which must be studied collectively. 



We are stimulated by ideas, but we live and advance by knowledge. 



Returning to the IMollusca with this thought in mind, we note that 

 during the year Yerrill has well-nigh demolished the long-languished 

 'schematic mollusk,' building up" a plausible argument for the 

 origin of the great groups of MoUusca from free-swimming forms 

 similar to the present veligers and pro-veligers. As concerning the 

 truth that the Polyplacophora are in respect to their bilateral 

 symmetry primitive, but in respect to the terminal anus highly 

 specialized, his reasoning is most forcible. Our conceptions of larval 

 forms of invertebrates have become less stereotyped with advancing 

 years ; and it may be remarked that since the appearance of Verrill's 

 paper a most beautiful study of the larvae of marine annelids has 



1 n. Fol, Arch. Sci. Phys. et Nat. Geneva, ser. Ill, vol. xxv, p. 393. Also Aunt. 



Anz., Bd. \T, p. 26(j, and Comptes Eeudiis Acad. Sci. Paris, torn, cxii, p. 877. 

 ' L. GiiisTinrd, Ann. Sci. Nat. Bot., ser. VII, torn, xiv, p. 163. 

 ' Cf. Wilson and Mathews, Journ. Morph., vol. x, p. 319 ; J. B. Farmer, Ann. 



Bot.. vol. vii, p. 393. 

 " Cf. J. B. Farmer, Sci. Procress, vol. i (n.s.), p. 141. 

 5 T. 11. Morgan, Arch. Entwick. Mech., Bd. iii, p. 339. 

 s A. E. ^"errill, Anier. .Journ. Sci., ser. IV, vol. ii, p. 91. 



