Hyatt.] 6Q [March 6 



and the act of fusion having become advantageous, we can under- 

 stand how it could be changed into conjugation for reproductive 

 purposes. The advantages of cross fertilization would secure pro- 

 gress in habits and structure until ultimately the differentia- 

 tion of highly specialized forms of the nuclei would take place and 

 the sexes would become distinguishable in unicellular animals. 

 We can also understand with the assistance of this theory how 

 the universal habit of cross fertilization might gradually have led 

 to the localization of sexual zoons in special parts of colonies, 

 forming primitive sexual organs in different colonies, thus taking 

 the final step towards the separation of the sexes, as they 

 appear among Metazoa, 



In his monograph of the Monera (Jena. Zeitschr., vol. iv, also 

 translation Journ. Micr. Sci., vol. ix, 1869), Haeckel describes the 

 frequent occurrence of fusion between two or more of the 

 amoeba-like young of Protomyxa aurantiaca in order to form lar- 

 ger individuals. 1 This author is uncertain whether the habit is a 

 part of the history of development, or is merely accidental, result- 

 ing from contact in feeding on the same morsel, etc., but favors the 

 latter supposition. The number of vacuoles, according to Haeckel, 

 appears to indicate the fusion of as many distinct amoeboid 

 forms, and as there are often several vacuoles in the bodies in 

 many groups of Protozoa, it is quite possible that fusion may be 

 more general than is supposed. This is evidently Haeckel's view 

 as may be read in his remarks with regard to Magosphaera (Jena. 

 Zeitschr., vol. vi, p. 18.). Among the Myxomycetes the formation 

 of a plasmodium is considered by Sachs as concrescence, and he 

 at the same time by his description makes it evident, that it is 

 precisely similar to the ordinary agamic fusion of amoeba-like 

 young of Protomyxa, that it is also undoubtedly followed by fruc- 

 tification, and, therefore, must be considered as a step in the 

 direction of true conjugation. The author's words are as fol- 

 lows : " there is absolutely no reason why the coalescence of the 

 Myxamoebae should not be regarded as a form of conjugation." 

 (Text Book of Botany, 2d Eng. Ed., 1882, p. 253.) 



1 Concresence is common, and many examples can be given among the Porifera, 

 but this is not properlv fusion. It is the union of multicellular bodies, aud we think 

 the term fusion should be limited to the more intimate blending of cells, or uni- 

 cellular zoons, the spermonucleus and feminucleus, etc. 



