ZOOLOGY — MORSE, NAPLES ZOOLOGICAL STATION, PEARL. 247 



Several local lists of the species secured, characteristic at that season of 

 the year of the different portions of the region traversed, together with notes 

 on their habits, have been prepared for convenience of reference. These 

 are accompanied by a series of photographs illustrating some of the typical 

 habitats in which they live. 



The body of the report consists of a complete annotated systematic list of 

 the species taken, with full data and descriptions of several forms new to 

 science. 



Naples Zoological Station, Naples, Italy. Grant No. 332. For niainte^imice 

 of hvo tables. (For previous reports see Year Book No. 2, p. CLiv, Year 

 Book No. 3, p. 145, and Year Book No. 4, p. 288.) $1,000. 



As in previous years, the grant was made to aid the laboratory in paying 

 for the maintenance of two research-tables. The director of the laboratory 

 assigned the tables during the past year to Dr. Naohide Yatsu and Dr. Ray- 

 mond Pearl. Abstracts of reports by these investigators will be found in the 

 following pages. 



Pearl, Raymond, University of Pennsylvania, Philadelphia, Pennsylvania. 

 Grant No. 345. Completion of mvestigatio7is by statistical vietJwds 07i 

 variation and correlation. (For previous reports see Year Book No. 3, 

 p. 140, and Year Book No. 4, p. 285.) $500. 



Abstract of Report.— tho^ year was spent in work at the following Euro- 

 pean laboratories : Zoologisches Institut, at Leipzig ; Biometric Laboratory, 

 University College, London ; and the Stazione Zoologica, at Naples. 



The following investigations were completed, and the papers detailing the 

 results will appear shortly : 



(i) A biometrical study of conjugation in Paramecium. The results of 

 this work may be summarized as follows : 



{a) It was demonstrated that the conjugant individuals of a Paramecium 

 population are distinctly differentiated in size and shape of body, both in 

 respect to type and variability, from the non-conjugant portion of the popu- 

 lation living in the same culture at the same time. 



{b) There is a high degree of homogamy in the pairing of individual 

 Paramecia in conjugation. Individuals like one another in size and shape 

 of body tend to conjugate together. 



{c) It was shown that this homogamy can not be accounted for either by 

 any form of random pairing or by a process of equalization in size after 

 conjugation has occurred. 



{d) A definite physiological basis for the homogamy is assigned, and it is 

 shown that the existence of homogamy in conjugation and the differentiation 

 of conjugants from non-conjugants have significant theoretical bearings in 

 the interpretation of the life history of Paramecium. 



