742 JOHN BEARD, 



needed for this result. The simplest arrangement is, however, that 

 under which each individual "produces" two kinds of gametes, and 

 under which these taken together make up four distinct categories. 

 As already pointed out, if these be of such a nature, that their 

 pairings be restricted, discriminated, and selected, the bringing-forth 

 of two kinds of individuals will be secured. 



In these lines the individuals have been vaguely spoken of with- 

 out attaching to them any particular attributes except unlikeness. 

 The conditions are not altered, when they are described as Metazoan 

 ones. The multicellular sterilised individuals, termed Metazoa, are 

 simply dimorphic forms (or including hermaphrodites polymorphic 

 ones), bearing gerra-cells, that is unicellular organisms, of a certain 

 category. The problem of sex, therefore, is not one referring directly 

 to the former, for these naturally bear a certain impress, male, or 

 female (or hermaphrodite), from the nature of the germ-cells harboured 

 by them. So that the individuals referred to above may be taken to 

 be the unicellular ones, the germ-cells. 



The cycle of life of these is really a double one, for it includes 

 four sorts of gametes, of which two are formed by one sort of germ- 

 cell and two by the other. The determination of sex for the following 

 generation must lie along the one line or the other; there would be 

 no order, were this not fixed and constant. It has come to be along 

 what we term the female line, for it is the egg, which develops, not 

 the spermatozoon. For this reason, although but three sorts of gametes 

 be needful for the continuation of two categories of individuals, two 

 of these must be ditferentiated along the female line. The third kind 

 remains to be formed along the other line, that of the male. As we 

 have seen, in some instances there are two sorts of gametes also 

 differentiated here, but of these only one is of functional value. 



It is owing to this circumstance, that the female has retained 

 the property of forming two sorts of functional gametes, and that 



still unanswered question, "wie konnte eine auf so schwachen Füssen 

 stehende Lehre unter den Zoologen bis heute sich unerschüttert er- 

 halten, ja fast als selbstverständlich hingenommen werden?" (in: Kosmos, 

 V. 2, 1885, p. 333). 



It may also be pointed out, that in hermaphroditism, where there 

 obtains a third sort of gamete, the male egg, there arises from the 

 fertilisation of this a second kind of individual, the complemental or 

 dwarf male, e. g., Sacculina, Myzostoma (some species), certain Cirri- 

 pedia and Nematoda, etc. 



