2 An Examination of Weismannism. 



all other modern theories of heredity — such as those of 

 Spencer, Hackel, Elsberg. Galton, Nageli, His, Brooks, 

 Hertwig, and De Vries — occupy positions more or less 

 intermediate between these two extremes. Therefore, 

 also, we need not wait to consider these intermediate 

 theories \ 



When closely analyzed, Mr. Darwin's theory — or 

 the " provisional hypothesis of Pangenesis " — will 

 be found to embody altogether seven assumptions, 

 namely : — 



i. That all the component cells of a multicellular 

 organism throw off inconceivably minute germs, or 

 " gemmules/' which are then dispersed throughout the 

 whole system. 



2. That these gemmules. when so dispersed and 

 supplied with proper nutriment, multiply by self- 

 division, and. under suitable conditions, are capable of 

 developing into physiological cells like those from 

 which they were originally and severally derived. 



3. That, while still in this gemmular condition, 

 these cell-seeds have for one another a mutual affinity, 

 which leads to their being collected from all parts of 

 the system by the reproductive glands of the organ- 

 ism ; and that, when so collected, they go to con- 

 stitute the essential material of the sexual elements — 



1 In as far as these sundry theories of heredity are not more or less 

 intermediate between those of Lanvin and Weismann, the differences 

 have reference either to points of comparative detail, or else to the 

 introduction of ideas derived from chemistry and physics — whereby it 

 is sought to show that the principles of chemical combination and of 

 rhythmic vibration may have a more or less considerable share in the 

 matter. For my own part I do not see that the introduction of such 

 ideas has been of any avail in helping — even hypothetically — to explain 

 the phenomena of heredity; and therefore I do not deem it worth our 

 vvhile to consider them. 



