ZOOLOGY — NAPLES ZOOLOGICAL STATION, WILSON. 22$ 



semination ; but Dr. Mark has made arrangements for the continuation of 

 that part of the work during the coming year. 



Naples Zoological Station, Naples, Italy. Grant No. 493. For mainte- 

 nance of two tables. (For previous reports see Year Books Nos. 2, 3, 

 4, 5, and 6.) $1,000. 



During the year the following American naturalists have been assigned to 

 tables in the Zoological Station: Prof. Alfred G. Mayer, from November 

 25, 1907, to February 2y, 1908; Dr. Elliot R. Downing, from February i to 

 May 25, 1908; Mr. Charles S. Mead, from April 28 to May 22, 1908; Dr. 

 Stewart Paton, from October 17, 1907, to June 27, 1908. 



Wilson, Edmund B., Columbia University, New York, New York. Grant 

 No. 370. Researches on the chromosomes of insects and other animals 

 with reference to the cytological basis of sex-production and Mendelian 

 inheritance. (For previous reports see Year Books Nos. 5 and 6.) $500. 



This grant was made only for the collection of material in 1906, but a part 

 of the work carried on since then has been based upon the material thus col- 

 lected. During the past year the work has been carried on by Professor 

 Wilson, Mr. F. Payne, and Mr. C. V. Morrill. 



Professor Wilson has completed and sent to press a study of the genus 

 Metapodius, which forms the fifth of his series of "Studies on Chromosomes." 

 This paper deals especially with forms that contradict the usual rule of spe- 

 cific constancy in the number of chromosomes. The study of an extended 

 series of material proves that the variation affects only a particular class of 

 chromosomes, the "supernumeraries," that undergo a variable distribution to 

 the gamete-nuclei, and hence produce corresponding variations in the zygotes. 

 Detailed analysis of the facts lends strong support to the hypothesis of the 

 genetic continuity of the chromosomes, and also affords new data bearing on 

 the problem of sex-production. 



The studies of Mr. Payne, made especially on the genus Galgidus and on 

 several genera of the reduvioid Hemiptera, have brought to light several new 

 and interesting types of sexual differences of the chromosomes. All of them 

 conform to the general principle, already established for other forms, that 

 half the spermatozoa are male-producing and half female-producing; but the 

 special modifications of the process are shown to be much more varied and 

 extensive than was at first supposed, and give valuable data in regard to the 

 manner in which the number of chromosomes changes from species to species. 

 A brief paper on the phenomena in Galgidus has been published in the Bio- 

 logical Bulletin for April. 1908, and a full presentation of the results on all 

 the forms studied is well advanced towards completion. 



Mr. Morrill's work has been devoted to a comparison of the chromosomes 

 in the oogenesis, fertilization and early stages of development of the egg with 

 those seen in the spermatogenesis. 



