April 1892.] THE BOTANICAL SOCIETY OF EDINBURGH. 411 



in Ulothrix, or in Fandorina. In Ulothrix the gametogonia 

 give rise to gametes, which vary in their number inversely 

 to their size, while in Fandorina each gametogonium gives 

 rise to eight gametes, large, medium, or small, as the case 

 may be. Supposing, now, that gametogenic divisions in a 

 species were inconstant, " broods of gametes would be formed, 

 whose size was inversely proportional to the number of the 

 brood, the extreme forms would be small, active gametes, and 

 large, sluggish ones respectively. As the latter are ill-fitted 

 to conjugate among one another in the struggle for pairing 

 [^wJiT/ ! .?], the small, numerous active ones would be most 

 likely to find pair with these large ones, and the rejuve- 

 nescence of such unions would be the more efficaceous, 

 because of the difference of temperament between the parent 

 gametes. The middle forms being produced in smaller num- 

 bers than the little gametes, and less useful either way, 

 would tend to disappear. The difference in size between 

 the micro- and mega-gametes would tend to increase, and a 

 division of labour take place, the megagamete tending to 

 accumulate nourishment, to give its zygote a good start, the 

 microgamete gaining activity and delicate sensibility, and by 

 this differentiation of temperament, the zygote would be the 



gainer. This I take to be the Origin of Sex." "I 



accept, then, one main thesis of the Evolution of Sex (Geddes 

 and Thomson), that male and female are distinguished by 

 their respective temperaments." 



If in this way binary sex, with its advantages, has been 

 developed, what then led to " Sex " being developed at all ? 



Hartog quotes Haberland's, Grliber's, and Elmer's obser- 

 vations on nuclei, and comes to the following conclusion : — 

 " We have ample direct evidence for regarding the apparently 

 ' resting ' nucleus in a cell as having the same sort of relation 

 to the cytoplast as a nerve-centre has to an organism, a view 

 supported, too, by the fact that the nucleus approximates in 

 chemical composition to nerve-substance, being richer in 

 lecithin and phosphorus generally than the cytoplasm. 

 Now, in ordinary cell-division, on the principle of con- 

 tinuity, there is no essential change in brood- cytoplast and 

 brood-nucleus, and the result of repeated cell-fission is 

 merely a multiplication of these. But we know that a 

 nerve-centre ceases to respond readily to a continued or 



