756 EEPORT— 1892. 



tiated genital ridge of the salamander shows that it is not specially related to the 

 spermatocytes ; while its appearance in cells so obviously primitive as the 

 leukocytes proves it to be in no way specially connected with the reproductive 

 elements, and suggests that it should be regarded rather as a normal constituent 

 of the resting cell. 



The ' attraction sphere ' of Flemming cannot represent in ioto those described 

 above, as it consists of a central body (or bodies) and its immediate radiation only, 

 apart from anything analogous to the detinite archoplasm which Hermann 

 describes. The complicated origin attributed to the spindle in the mutually 

 irreconcilable descriptions of previous authors is, moreover, much simplified by the 

 study of the cells in the same genital ridge. The intim.ate connection between the 

 ' Nebenkern ' and spindle described by Platner in the spermatocytes of Helix ia 

 most strikingly borne out during the metamorphosis of these cells. The central 

 bodies become duplicated ; the two halves recede from one another through the 

 archoplasm, whose mass elongates in the direction of their motion. 



The delicate external radii of the cell mass follow the central bodies as specific 

 centres while en route to the polar extremities of the archoplasm; until, simul- 

 taneously with their arrival in this position, these radii assume the characters of 

 the well-known astral radiations. 



The whole spindle is formed from the intervening archoplasmic mass, and 

 apparently from nothing else. 



So soon as the constriction to form the daughter-cells becomes apparent, the 

 expanded spindle fibres collect around the intermediate bodies of Flemming, and 

 by their fusion regenerate an archoplasm on either side of the last division planes 

 of the cells. The central bodies enter into a secondary connection with these new 

 archoplasms, travelling up the fibres which remain between them and the concavi- 

 ties of the daughter nuclei. It thus appears that in these various cells of the 

 vertebrate (Salamondra) Platner's generalisation with respect to the cells of the 

 invertebrate {Helix), that ' zwischen Kniiuelgeriist, Spindelfasern imd Nebenkern 

 ein genetischer Zusammenhang existirt,' is strikingly extended and borne out. 



Oa an Abnormal Horse's Foot. By Professor J. Cossar Ewart. 



G. The Origin of Sex. By Gcistav Mann, M.B., G.M.^ 



AVhile studying the origin of sex, two distinct points must always be kept in 

 ■view — first, the origin of sexual cells ; and secondly, the physiological cause 

 determining the sex of potential sexual cells. 



With Ryder and Hartog the author believes that sexual cells are derived from 

 * Zoosporangia,' as a common origin of male and female cells seems to be proved by 

 the reduction in the number of chromatin segments which occurs in both male and 

 female cells previously to the act of fecundation. 



The author holds, further, that any condition unfavourable to a ready assimila- 

 1 ion of food will produce a male organism ; while, reversely, any condition favouring- 

 the assimilation of food will tend to produce a female organism. 



Conjugation of two cells is, then, equivalent to the new-formation of one cell 

 thus constituted, that a common trophic centre is formed which is capable of exert- 

 ing its influence over the various oi-gans, and that its organs are able to maintaia 

 the trophic centre by satisfying its chemical affinities — i.e., its hunger. 



The author does not believe, therefore, the active male cell to effect the restoration 

 of the equilibrium, as manifested by the division of the passive female cell, by acting 

 either as a ferment (v. Sachs), or by simply doubling the amount of chromatin in 

 the female cell (Strasbm-ger, Weismann, Eyder), or by being the carrier of 

 katastates ((leddes and Thomson), or by restoring the susceptibility of the female 

 nucleus to stimuli from its own cytoplasm (Hartog) ; nor have we digestion of the 



' For a full accocnt of author's views gee ' The Embiyo-sac of Myosuru^ 

 minimits, L.,' Trans, and Proc. of But. Soc, Edinhurgh, July 1892. 



