4 6; 



tribution to onr knowledge of causal connection in organic 

 nature. Leipzig, 1873. 



50 (i. 178). The Process of Fertilization has been very 

 variously viewed, and was formerly often regarded as an 

 entirely mysterious process, or even as a supernatural miracle. 

 It now appears no more " wonderful or supernatural " than the 

 process of digestion, of muscular movement, or of any other 

 physiological function. For the earlier views, cf. Leuckart, 

 Article " Zeugung " (generation) in R. Wagner's " Dictionary 

 of Physiology," 1850. 



51 (i. 179). Monerula. The simple, very transient, kernel- 

 less condition, which we briefly call the * monerula," and, in 

 accordance with the fundamental law of Biogeny, regard as 

 palingenetic reproduction of the phylogenetic Moneron parent- 

 form, appears to vary to some extent in different organisms, 

 especially in the matter of duration. In those cases in which 

 it no longer occurs, and in which the kernel of the fertilized 

 egg persists wholly or partially, we may regard this phenomenon 

 as a later, kenogenetic curtailment of Ontogeny. 



52 (i. 181). The Plasson of the monerula appears, mor- 

 phologically, a homogeneous and structureless substance, like 

 that of the Moneron. This is not contradicted by the fact that 

 we ascribe a very complex molecular structure to the plastidnles, 

 or " plasson-molecules," of the monerula; this latter will 

 naturally be more complex in proportion as the organism which 

 it ontogenetically constitutes is higher, and as the ancestral 

 series of that organism is longer, in proportion as the preceding 

 processes of Heredity and Adaptation are more numerous. 



53 (i. 182). The Fundamental Significance of the Parent-cell, 

 or cytula, as the foundation-stone of the young organism in the 

 course of development, can only be rightly appreciated, if the 

 part taken in its constitution by the two generating cells ia 

 rightly appreciated, the part taken by toe male sperm-cell and 

 by the female egg-cell. 



54 (i. 183). The One-celled Germ-organism, like the act of 

 fertilization from which it results, has been very variously 



