June 7, 1907] 



SCIENCE 



911 



cytes themselves, which, as they become more 

 numerous, tend to migrate to the surface of 

 the egg and finally form into one or more 

 layers. Each nucleus apparently acquires a 

 local area or zone of protoplasm which ulti- 

 mately becomes marked off from adjacent 

 areas as more or less of a definite cell. The 

 pigment of the egg accumulates around the 

 boundaries of the more superficial areas, which 

 thus appear to be sharply delimited, as seen 

 in sections under the microscope. Although 

 the internal mass of yolk contains numerous 

 nuclei, frequently imdergoing amitotic divi- 

 sion, the central mass of the eggs remains in 

 a syncitial condition for considerable time. 



I am inclined to believe that, in some cases 

 at least, the female pronucleus of the egg takes 

 no part in this cell proliferation, because I 

 have been able to find in sections in several 

 instances a comparatively large clear proto- 

 plasmic zone, variously placed in the egg, 

 which, although invaded more or less on all 

 sides by nuclei, itself remains undivided, and 

 in it is visible what appears to be a degener- 

 ating nuclear-like structure, presumably the 

 remainder of the female pronucleus. 



Many eggs show no development, but this is 

 not to be wondered at, since doubtless a num- 

 ber of them, although pricked, received no 

 corpuscles from the orifice of the capillary 

 tube. Other eggs, presimiably not fully ready 

 for fertilization, did not develop; although 

 the corpuscles apparently proliferated exten- 

 sively, they later ran together to form giant 

 cells and frequently seemed to become phago- 

 cytic in nature. In still other cases, what 

 seemed to be phagocytosis was visible on one 

 side of the egg, while on the other side the 

 nuclei appeared to be ranging up into a defi- 

 nite cellular layer. A detailed description of 

 the experiments is in preparation. 



Michael F. Guyeb 



The Univeesitt of Cincinnati, 

 May 13, 1907 



TRANSMISSION INHERITANCE DISTINCT FROM 

 EXPRESSION INHERITANCE^ 



Conjugations of sex-cells of higher plants 

 and animals have two results, an intermediate 



^ Read before the Botanical Society of Washing- 

 ton, April 13, 1907. 



and a final product. The intermediate prod- 

 uct of conjugation is a new organism, the 

 final product a new equipment , of sex-cells. 

 The new organism is built up by vegetative 

 subdivisions of the conjugating pair of sex- 

 cells. The conjugation is not completed until 

 the new generation of sex-cells is to be formed. 

 Fertilization is the beginning of the process 

 of conjugation, which may not conclude for 

 months or years after fertilization has taken 

 place. The organism which is built up during 

 conjugation may be called a conjugate organ- 

 ism, or conjugate. It belongs to the same 

 generation as the sex-cells which initiate the 

 conjugation. The next generation may be 

 called perjugate, since it has passed through 

 the conjugation of the preceding generation 

 and represents its completed results. 



When sex-cells of diverse parentage are as- 

 sociated in conjugation the organisms they 

 build up (conjugates) may be like one parent, 

 or like both parents, or intermediate between 

 the two parents, or different from either 

 parent. The same latitude of alternatives of 

 expression is found in the perjugate gen- 

 eration. The crossing of two varieties of 

 pink-eyed mice yields black-eyed conjugates. 

 Two varieties of smooth-seeded cottons gave 

 smooth-seeded conjugates, but woolly-seeded 

 perjugates. Such instances prove that the 

 expression-tendency of a gamete can be 

 altered by association with another gamete 

 of diverse parentage. Either the conjugate 

 generation or the perjugate generation, or 

 both, may show characters which neither of 

 the parent gametes would have brought into 

 expression if it had secured a partner of its 

 own kind. There is no corresponding proof 

 that transmission inheritance is altered by 

 such associations. The reappearance of such 

 characters as the black eyes and the woolly 

 seeds, which have been abeyant through many 

 generations, shows that failure of expression 

 does not prove failure of transmission. 



Transmission inheritance may be thought of 

 as the dial of a compass which carries many 

 character-directions, though the needle of ex- 

 pression points to only one. This expression- 

 polarity is called dominance in conjugate 

 organisms and potency in gametes. Nobody 



