110 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
AN of these must, according to 17, 25, and 26, be considered as 
determined by the unknown (molecular?) structure and activities of 
the protoplasm. 
31. It follows from 30 that the early development of Asplanchna, to 
a stage somewhat beyond gastrulation, may be analyzed into two fac- 
tors: (1) the influences determining and preserving the form of the 
egg as a whole, and (2) processes occurring in consequence of the spe- 
cific (molecular ?) structure and activities of the protoplasm, 
Both of these factors, which perhaps should be considered as different 
manifestations of one, are from a causal-mechanical standpoint, entirely 
unknown. “Damit werden die causalen Bedingungen der Entwicklung 
vorzugsweise in das Moleculargeschehen verlegt und entziehen sich 
vorderhand grossentheils unserer weiteren Erforschung.” (Roux, '85*, 
p. 427.) 
