944 



SCIENCE 



[N. S. Vol. XXVII. No. 703 



description of the structure of a penna- 

 tulid. (MonograplL in progress.) 



On the Distribution of Certain Salmomidce 

 in Wisconsin: Geoege Wagner, Uni- 

 versity of Wisconsin. 

 A discussion of the occurrence of the 

 lake trout and certain Coregoni in Wis- 

 consin, with special reference to the phys- 

 ical characters of the lakes concerned. 



The Process of Heredity as Exhibited by 

 the Development of Funduhis Hybrids: 

 H. H. Newman, University of Michigan. 

 In the spring of 1905 the writer, after 

 familiarizing himself with the experi- 

 mental work on heredity of the last decade 

 or so, came to the conclusion that this work 

 dealt too exclusively with definitive char- 

 acters and scarcely at all with the origin 

 and development of these characters. Be- 

 ing firmly convinced that heredity is essen- 

 tially a developmental phenomenon, it 

 seemed necessary to make a study of the 

 process of heredity as exhibited in living 

 embryos, watching for the origin of char- 

 acters and studying their development in 

 pure bred and hybrid forms. 



Very favorable material was found in 

 two species of killifish, Fundulus hetero- 

 clitus and F. majalis. These offered suf- 

 ficiently wide differences morphologically 

 and physiologically, in eggs, embryos and 

 adults, for experimental study. The most 

 important diiferences for the study of 

 heredity in early development were dif- 

 ferences in size and protoplasmic content 

 of the ova; in time rate of development; 

 in quality, distribution and time of appear- 

 ance of pigment ; in rate and time of estab- 

 lishment of the heart rhythm; in resist- 

 ances to unfavorable conditions; and the 

 inter-influences of these and other char- 

 acters. 



The following are some of the results 

 obtained : 



1. The influence of the sperm of the less 



rapidly developing species showed a meas- 

 urable retarding effect upon the egg of the 

 more rapidly developing species in a com- 

 paratively short time, usually after about 

 eighteen hours, at which time the blastodisc 

 is beginning to spread out over the yolk. 

 In the reciprocal cross there was a some- 

 what later, but just as marked, accelera- 

 ting effect. 



2. The influence of maternal and pater- 

 nal factors was 'uot of constant potency, 

 but alternating waves of parental influence 

 emphasized the fact that heredity is 

 essentially a process involving rhj^thms of 

 parental influence and constant flux of 

 characters. 



3. Certain dominant and hyperdominant 

 characters were shown to be the secondary 

 physiological effects of a primary blending 

 of characters, or, as the necessary result of 

 mere mechanical restrictions, such as size 

 of egg membrane or amount of yolk avail- 

 able. 



4. In order to avoid all sorts of complex 

 and contradictory conditions, it was found 

 necessary to equalize the physiological con- 

 ditions of the parents. Only males and 

 females freshly brought in and at the 

 height of their spawning activities, would 

 give even approximately uniform results 

 in different experiments. 



5. It was also found necessary to 

 equalize the environmental conditions of 

 developing embryos. Otherwise highly 

 complex conditions arose that obscured the 

 study of heredity. 



6. In view of the fact that external 

 factors, such as physiological condition of 

 parents and environmental conditions of 

 embryos, showed such a marked influence 

 in disturbing the process of heredity, it 

 seems necessary to emphasize the potency 

 of external factors in heredity. Heredity 

 seems to be in essence a developmental 

 process, determined partly by the archi- 

 tecture of the germ-plasm and partly by 



