106 



SCIENCE. 



[N. S. Vol. XXV. No. 



marks were illustrated by a number of lantern 

 slides taken during the field courses given by 

 him at Axton, in the Adirondaeks, for the 

 Cornell School, and at Milford, Pa., for Tale 

 University. 



The third paper, ' A Kecord of the Black 

 Rat in Virginia,' was read by Mr. William 

 Palmer. He noted the occurrence of an iso- 

 lated colony of the black rat (Jftjs rattus) on 

 the top of a Virginia mountain, Peaks of 

 Otter, in Bedford County, at an elevation of 

 3,875 feet. The specimens collected are not 

 quite typical. Probably but few individuals 

 now exist in and about an old store at the 

 summit. 



The 421st meeting was held on December 

 1, 1906, President Knowlton in the chair and 

 about fifty persons present. 



General T. E. Wilcox remarked on the un- 

 usual abundance of quail and the cottontail 

 rabbit in New York a few miles south of 

 Utica. 



Dr. Evermann informed the society of the 

 recent death of two naval ofiieers to whom 

 biological science is much indebted. Lieuten- 

 ant Eranklin Swift, retired, of the steamer 

 Fish HawTc, and Lieutenant-Commander Leroy 

 M. Garrett, of the. Albatross. Lieutenant Swift 

 died on November 10, at Charleston, S. C, 

 of typhoid fever, and Lieutenant-Commander 

 Garrett was washed overboard 500 miles north- 

 west of Honolulu on November 21, while the 

 Albatross was returning with the great collec- 

 tions of the trip to Japan. These officers have 

 commanded these research vessels during some 

 of their most important work and are in large 

 part responsible for the excellent results ob- 

 tained. 



Dr. L. O. Howard presented the first paper, 

 on the subject ' Polyembryony and Fixation 

 of Sex.' This paper was published at length 

 in Science, December 21, 1906. 



The second paper consisted of an illustrated 

 lecture by Mr. John W. Titcomb, on 'Prin- 

 ciples and Methods in Fish Culture.' He 

 explained the underlying principles of artifi- 

 cial propagation as applied chiefiy to salmon- 

 oid fishes, described in detail the methods and 

 manipulations concerned and illustrated every 



point by lantern-slide pictures, showing appa- 

 ratus, operations and the fishes themselves in 

 all stages from the egg upward. He com- 

 mented on the relation of fish culture to va- 

 rious natural sciences. The long and inter- 

 esting series of illustrations included pictures 

 showing the inauguration of fish culture by 

 the speaker in Argentina, South America. 

 M. C. Marsh, 

 Recording Secretary 



DISCUSSION AND CORRESPONDENCE 



POLYEMBRYONY AND SEX-DETERMINATION 



In an extended review in the last number 

 of Science (December 21, 1906), Dr. Howard 

 has emphasized the astonishing and valuable 

 results of the recent work by Marchal ('98, 

 '04) and Silvestri ('05, '06) on the spon- 

 taneous polyembryony of certain parasitic 

 Hymenoptera. He has quoted Bugnion's dis- 

 cussion of the bearing of this work on sex- 

 determination but has not called attention to 

 the fact that in the light of Silvestri's work 

 this view may need revision. 



As stated, Bugnion, '91, in the course of 

 his work upon Encyrtus had noted that as a 

 rule all of the individuals emerging from one 

 host belong to a single sex. At the time, 

 Bugnion thought that this " should be at- 

 tributed to an occasional parthenogenesis, the 

 caterpillars giving birth exclusively to males 

 having been those which had been pierced by 

 a non-fertilized Encyrtus." 



This conclusion, which was a logical one in 

 view of the data then at hand, Bugnion dis- 

 cards completely since the appearance of Mar- 

 ehal's work. He believes that the phenomenon 

 must be " a natural consequence of poly- 

 embryony, and that one would expect the 

 sexes to be separated in this way wherever 

 the embryos come from the division of a 

 single egg." 



While the latter clause is undoubtedly true, 

 the possibility of the facts being explained 

 on the basis of parthenogenesis is by no means 

 excluded. Bugnion, in his work, did not ob- 

 serve the oviposition. Marchal presents no 

 evidence that parthenogenetic development 

 does not take place. In fact, he purposely 

 leaves the question open, as '04, p. 298, " Le 



