Decemuer U, 1003.] 



SCIENCE. 



741 



doubt is partly responsible, as ■well as the 

 long time required for a thorough course. 



The number of scientific students is still 

 on the increase. In most of the other 

 faculties there have been no consistent 

 gains or losses, the decrease in certain uni- 

 versities being made up by a corresponding 

 increase in others. Columbia University 

 still has the largest eurohuent in the grad- 

 uate schools, with Chicago second, Harvard 

 third and Yale fourth. The University of 

 ^lichigan continues to head the list in the 

 number of law students, followed by Hai'- 

 vard. Minnesota and Columbia in the order 

 named. Although the attendance at the 

 Columbia medical school has suffered a loss 

 of over 100, this university still has the 

 largest enrolment of any of the medical 

 schools enumerated, but is closely followed 

 by Illinois, with Northwestern and Penn- 

 sylvania occupying third and fourth places 

 respectively.* As to the scientific schools, 

 Cornell is in the lead, with Yale second, 

 California third and Michigan fourth. 

 Harvard has by far the largest collegiate 

 enrolment and also had the largest summer 

 session last year. As to the relative rank- 

 ing of the teaching force in the largest in- 

 stitutions, Columbia now occupies first 

 place, with Harvard second, Cornell third 

 and Illinois fourth. 



Rudolf Tombo, Jr., 



Eegistrar. 



CoLUMBi.v University. 



TARIATIOXS INDUCED IN LARVAL, PUPAL 



AXD IMAGINAL STAGES OF BOMIiYX 



MORI BY COXTROLLED VARY- 



/A"0 FOOD SUPPLY. 



OxK of the races of the mulberry silk- 

 worm, liombyx mori, has been the subject 



* The table credits Columbia and Illinois with 

 609 students each, but in the case of Cohimbia 

 there are a number of fourth-year college students 

 enrolled in the medical school who do not appear 

 among the OCfl, hut in the primary registration 

 under the college. 



of experiments directed toward a determin- 

 ation of the exact quantitative relation 

 which quantity and quality of food Ijear to 

 the development and variations of the indi- 

 vidual insect and its progeny. Such an 

 experiment, on the face of it, might seem to 

 be a laborious task having no further justi- 

 fication than the superfluous, though 

 specific, demonstration of the axiom that 

 the well-nourished are the well-developed. 

 The writers will not hesitate, however, to 

 put on record authentically determined 

 data showing just how definite and con- 

 stant is the relation for one animal species 

 between varying nutrition and variations. 

 As a matter of fact the experimental breed- 

 ing and rearing and the accumulation of 

 quantitatively determined data refer to 

 several problems besides the few discussed 

 in this paper. The successive j^ears of 

 breeding have left us at the present mo- 

 ment with a large number, several thou- 

 sand, of eggs, due to hatch next JIarch, 

 which are the results of selected mating, 

 and of which the ancestors for two or three 

 generations are known, quantitatively de- 

 scribed, and preserved for reexamination, 

 if necessary. In addition to the knowledge 

 of the structural and physiological char- 

 acters (duration of various life-stages, etc.) 

 of these ancestors, the quantitatively deter- 

 mined life-conditions, normal and experi- 

 mentally varied, are known. These thou- 

 sands of the fourth generation should 

 afford us exact evidence, for this animal 

 species, touching the prepotency of sex, of 

 sports, of i)articular characters and of 

 vigor, as well as evidence regarding fertil- 

 ity in relation to age, and evidence concern- 

 ing genetic and physiological selection. 



The present statement is limited to an 

 outline of the results of only those experi- 

 ments relating directly to the influence ex- 

 erted by varying conditions of food supply. 



The insect, Bombyx mori, has a complete 

 metamorphosis, taking no food as an adult. 



