298 ERNEST WARREN. 



are clearly not ectodermal, and a number of other cases could 

 be cited. 



From tlie course of development previously described it 

 can be seen that the hereditary tendencies can be passed on 

 unimpaired through a considerable amount of budding, and 

 then after the blastomeres have divided into quite small cells 

 it seems to be a matter of indiiference how many of them are 

 enclosed in the thick cercaria-cyst ; the excluded cells perish, 

 the enclosed mass will develop into the embryo. Hence up 

 to this period there is no sorting out of hereditary tendencies 

 (except that sometimes the fundament of the cirrus-sac 

 appears quite early) into separate cells, but they reside in the 

 mass as a whole as they would in the body of a protozoon, 

 and are not separated out into distinct elements. The mass 

 of cells enclosed by the cercaria-cyst and beginning its 

 development should be regarded as an unit, and not as a cell- 

 republic. 



However special and obscure this development may be 

 held to be, yet the very fact that such a mode is possible, in 

 that the various organs appear direct in the homogeneous 

 mass of cells without the intervention of germ-layers, seems 

 to the author to demonstrate, in the words of Sachs,^ that 

 " cell formation is a phenomenon very general, it is true, in 

 organic life, but still only of secondary significance ; at all 

 events, it is merely one of the numerous expressions of the 

 formative forces which reside in all matter, — in the highest 

 degree, however, in organic substance." 



The Explanatory Abbreviations. 



ap. ? aperture of flame-cell. b. Section of the body of the encysted 

 animal, b. c. Branched cells, b. p. Basal portion of the flagellum. bd. Bud 

 from sporocyst. bm. Blastomeres. c. Cirrus, c. g. Cerebral ganglion. 

 c. cy. Cercaria-cyst. c. m. Circular muscle, c. s. Cirrus-sac. c. v. s. Cells 

 to form vesicula seminalis. c. w. Cyst -wall. cuv. Cavity of flame-cell. cce. 

 Gut-CKCum. cor. Cortex, cy. Adult cyst. cy. c. ? cystogen cells of embryo. 



* Sachs, Julius von, ' Lectures on the Physiology of Plants,' translation 

 by H. Marshall Ward, 1887, p. 73. 



