BODY SIZE AND CELL SIZE 



165 



a. Body size. I have studied in some detail the body size and 

 cell size of four species of the genus Crepidula, as well as of sev- 

 eral species of other prosobranch gasteropods. The mature 

 females of Crepidula are always larger than the males and are 

 firmly attached to some object from which they are unable to 

 move; the males on the other hand are smaller and have greater 

 power of locomotion. In the following measurements of body 

 size and cell size the two sexes were always carefully separated; 

 twenty mature individuals of the same sex were chosen and, after 

 having been removed from their shells, they were placed upon 

 blotting paper to remove any excess of water and were then 



TABLE 1 



Body size in the genus Crepidula 



ACTUA-L VOLUME OF 

 BODY 



Male 



C. convexa 0.01 



C. adunca 0.025 



C. plana j 0.046 



C. fornicata ! 1 . 25 



Female 



0.05 

 208 

 I 0.667 

 1.60 



RELATIVE VOLUME IN 

 SAME SPECIES OF 



Male 



Female 



5.0 



8.3 

 14.5 

 1.34 



RELATIVE VOLUME IN 

 DIFFERENT SPECIES 



Male 



1.0 

 2.5 



4.6 



125.0 



Female 



1.0 



4.16 



13.34 



32.00 



dropped into a known volume of water in a graduated tube; in 

 this way the average body volume of the twenty specimens was 

 determined. 



6. Tissue cells. Various tissue cells from corresponding organs 

 and parts of organs of C. convexa, C. plana, and C. fornicata have 

 been measured with the Zeiss 1/1 micrometer eyepiece and 3 

 mm. homogeneous immersion objective. The average dimensions 

 of such cells are given in table 2, and these measurements show 

 plainly that there is no constant correlation between body size 

 and cell size in these different species; the size of many tissue cells 

 is practically the same in all species (e.g. most of the epithelial 

 cells) while in those cases where the cell size differs in different 

 species, the larger cells are not always found in the species of 

 larger body size. Certain cells vary so much in size, especially 



