20 GEOEGE JOHN EOMANES 1875 



a Friday evening lecture at the Eoyal Institution on 

 his work on Medusae. 



He was also at this time working on the subject 

 of ' Pangenesis,' * and a series of letters to Mr. 

 Darwin and to Professor Schafer may interest some 

 readers. 



1 The following extract from ' An Examination of Weissmannism,' 

 ■pp. 2, 3, will, possibly explain the theory of Pangenesis, which assumes : 



1. 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 organism ; 

 and that, when so collected, they go to constitute the essential material of 

 the sexual elements — ova and spermatozoa being thus aggregated packets 

 of gemmules, which have emanated from all the cells of all the tissues of 

 the organism. 



4. That the development of a new organism out of the fusion of two 

 such packets of genirnules is due to a summation of all the developments 

 of some of the gemmules which these two packets contain. 



5. That a large proportional number of the gemmules in each packet, 

 however, fail to develop, and are then transmitted in a dormant state to 

 future generations, in any of which they may be developed subsequently, 

 thus giving rise to the phenomena of reversion or atavism. 



6. That in all cases the development of gemmules into the form of 

 their parent cells depends on their suitable union with other partially 

 developed gemmules which precede them in the regular course of 

 growth. 



7. That gemmules are thrown off by all physiological cells, not only 

 .luring the adult state of the organism, but during all stages of its develop- 

 ment. Or, in other words, that the production of these cell-seeds depends 

 upon the adult condition of parent cells, not upon that of the multi- 

 cellular organism as a whole. 



