BARR ON ASEXUAL DIMORPHISM. 13 



iixed iiulividiial, I'use wiih i(. This is ((nijugatiou, but conjugation is, 

 in effect, a sexual process and we have here the anahjgues, at least, of 

 sexual elements, in \\hi<h tlif sedentary individual represents the ovuiu 

 and the free one Ihe siicrni. 



In the oreuarines we have an asexual multiplication that is exceedingly 

 suggestiAe. In these, as well as in other forms, reproduction may con- 

 sist in splitting up Ihe body into a multitude of individuals. This 

 obviously secures a gicater uuuiIkm' of chances in the lottery of life. 

 In olher forms, the entire protoplasm grows fat, rounds up and secretes 

 a thick covering that may protect it during the time when the growth- 

 rythm. from external causes, must be suspended. Thus, on the other 

 hand, is increased the individual chance in the same struggle for 

 existence. 



We huA'e here, then, two forms of asexual reproduction, each affording 

 ^'ssential characters of sex-cells. Let us examine them further. In 

 Volvox, under unfarorahJe ('on(Jiti())is, both methods \ni\y occur, though 

 union between the two is today necessary for continuiMl existence. i>id 

 not these two methods originate as a means of tiding over, asexually, 

 an unfavorable time by embracing both the possibilities indicated above? 

 Some individuals of the colony are nourished at the expense of the rest 

 that they nuiy be strong to resist. Others are broken into minute, 

 flagellated individuals that they nmy, by their dispersion, find an environ- 

 ment where, with the lesser demand of their smaller body, they may eke 

 out a miserable existence. If, however, asexual dimorphism has ever 

 thus obtained in Volvox it has ceased to do so today for- sexual union 

 has come to be the necessary rule; and yet a careful comparison of the 

 individual cells of a single hermaphrodite colony seems to afford ground 

 for suspicion, at least, that the view above suggested may be essentially 

 a true one. 



(A.) A single zooid. poorly nourished, divides into many actively 

 motile cells that become male or fertilizing cells. 



(B.) A single zooid separates from the colonial complex and by 

 ordinary repeated division forms a colony asexually. 



(C.) A single zooid, better nourished at the expense of its neighbors, 

 grows into a large, sluggish or passive cell, the ovum or female cell. 



The second type (B) intermediate in size and activity, may well repre- 

 sent both extremes, preserving the original method of growth, while 

 the colony calls into use the others, involving specialized germ-cells, 

 only when it must otherwise fail to secure perpetuity. 



Certain phenomena in the reproductive processes of Amoeba are very 

 suggestive here, ^pore formation and the condition of encystment may 

 well represent the methods just discussed, though it has never, so far 

 as I am aware, been suggested that this has any sexual significance. 

 Of course this is not sexual differentiation; we simply have the condition 

 that has been overpassed by others, as perhaps Volvox, in true sexual 

 evolution. Does it not, however, suggest the primitive potentiality of 

 their so developing before the habit of union had become fixed? 



Reproduction as it exists in the metazoa has been of slow growth. 

 Arising in the protozoa from equal binary fission, smaller buds were 

 next set adrift. In turn, certain individuals in a somewhat integrated 

 colony were specialized for this purpose and ultimately grotips of cells 



