1884.] 67 [Hyatt. 



In the lowest form of conjugation which appears, in such 

 plants as Spirogyra, described by Sachs and others we find that 

 complete fusion of the cell contents or equal hermaphroditic 

 conjugation takes place, as it does in some Flagellata as shown 

 by Drysdale and Dallinger and others. In the next stage bisex- 

 uality appears, the nuclei become differentiated, and there is an 

 exchange between individuals, which may be and probably is 

 partial as supposed by Hertwig and Engelmann, the masculo- 

 nuclei or peripheral nuclei, being the essential parts of the 

 nucleus, which are transferred from one individual to another. 

 This condition, which is that of unequal hermaphroditic con- 

 jugation introduces that in which the male or so-called nucleolar 

 elements become preponderant in certain zoons more than in 

 others, and these zoons in consequence assume characteristics of 

 true males or microgonids such as are described by Butschli and 

 Engelmann among Protozoa. 1 This is a primitive condition, and 

 yet it has the essential characteristics of the function of impreg- 

 nation as it occurs thoughout the animal kingdom. We can 

 readily imagine this series with all its attendant phenomena, 

 and consequent differentiation of sex arising from any ine- 

 quality in the causes affecting the habits of the zoon, which 

 would thus acquire also the more active habits and desires of 

 the male, or the more passive and receptive habits of the female. 



The next stage in this line of morphogenesis would lead 

 into Metazoa where rapid growth and concentrated development 



1 We have found, also after farther examination of the literature, that Ferdinand 

 Cohn in Comptes Rendu s, Dec. 1856, p. 1054, and in notice of same (Ann. Mag. Nat. 

 Hist. ser. 2, vol. xix, 1857, p. 187), has described male and female cells in Volvox, and 

 also the division of the male cells into " spermatozooids." Also the mode of fertilliza- 

 tion of the females by the spermatozooids through impenetration, and union with 

 nuclei within. He has also described the greater size of the females, which is a notable 

 point in Butschli's comparisons. The descriptions and figures by Carter (Ann. Mag.< 

 Nat. Hist., ser. 3, vol. n, 1858), show that the male cells of Eudorina before, during, and 

 after division compare closely with the aspect of ordinary spermatocysts among Meta- 

 zoa. The bodies are gathered at the periphery in one hemisphere of the cyst and the 

 tails occupy the other or protoplasmic end, thus at once raising the question, whether 

 the bodies are not from nuclei, and the tails protoplasmic in origin as in Metazoa ? In 

 a subsequent article (ser. 3, vol. in), the same author also describes the male and female 

 colonies of Eiidortna. In giving Butschli credit as above, it must, therefore, be con- 

 fined to the homologies of the ovum and the female cell in Eudorina and Volvox, and 

 the spermatoc} r st and male cells, and also the effects of fertilization and the general 

 comparisons which we note farther on. 



