152 BIOLOGICAL LECTURES. 



young by perpetual rejuvenation and subsequent differentia- 

 tion, and therefore in no sense a peculiar substance. 



Every purely corpuscular theory, meaning thereby the phys- 

 ical transmission of gemmules, biophors, pangenes, or any other 

 supposed organic bearers of characteristics, must not only 

 account for a difficulty as great as that of the camel and the 

 needle's eye, but must also account for putting the numberless 

 characters, derived from the entire caravan of its immediate 

 progenitors and remote wild ancestors and their progenitors, 

 back to the origin of the phylum through the same narrow 

 tunnel. 



One has to imagine the corpuscles and all this active circula- 

 tion and concentration taking place invisibly, and yet requiring 

 visible vehicles of transmission in the minute spermatozoon and 

 nucleus of the ovum. Then he must picture their redistribution 

 over the body of the offspring, the larger number remaining 

 latent until the proper time arrives for them to develop, and 

 then locating themselves and coming out in exactly the right 

 place, or repeating at the right time some tendency or habit of 

 the ancestors. 



One is naturally led to ask how these particles acquired their 

 peculiar tendencies which force organisms along predetermined 

 paths of development, reproducing similar successive stages of 

 development with automatic regularity and repeating with more 

 or less precision the permanent stages of their ancestors ? In 

 what way did they acquire their wonderful ability to remain 

 latent until they had reached the proper place, and then measure 

 time so as to wake up and go to work at the right moment ? 

 The corpuscular hypotheses provide supposititious vehicles of 

 transmission, but they do not explain how or why these move 

 in their apparently predetermined cycles of change. 



Nussbaum's and Minot's 1 theory of panplasm or the con- 

 tinuity of germ plasm seems to be a necessity, if the transmis- 

 sion of germ particles or of organic atoms is rejected. Minot's 



1 Nussbaum, " Differenzining d. Geschlechts in Thierreich," Arch. f. mikr. 

 Anat., Bd. xviii, 1880, pp. 1-121. 



Minot's " Vererbung u. Verjiingung," Biol. Centralb., Bd. xv, 1895; and ibid., 

 American Naturalist, vol. xxx, 1896, pp. 1-9, 89-101. 



