256 



JOHN W. SCOTT. 



Another series of tests was made in order to demonstrate the 

 changes in density at different stages of development. See 

 Table II. It was shown that very young eggs, those that had 



TABLE II. 



To SHOW THE CHANGE IN DENSITY AT DIFFERENT STAGES IN THE DEVELOPMENT 



OF EGGS. 



attained one fourth the size of mature eggs and in which there w r as 

 not very much yolk laid down, had a specific gravity less than 

 1.070 (Fig. I, c). In a word, the density of the egg as a whole 

 is very noticeably increased as the yolk accumulates. It w r as 

 also learned that allowing the deposited eggs to stand in sea- 

 water for some time slightly increases their density (test 38). 

 During segmentation and the formation of the segmentation 

 cavity, the density grew less as one might expect (tests 41, 47). 

 It probably continues to decrease slightly, at least as far as the 

 late trochophore stage (test 57). My experiments did not carry 

 the work further than this point. 



Before the worm used in the first tests mentioned above, was 

 through depositing eggs, the surface of its body was wiped dry 

 and the ccelome was opened allowing the contents to escape into 

 a clean glass dish. An examination with the microscope showed 

 that the coelomic fluid contained corpuscles and eggs in various 

 stages of development, some being mature. Tests 32 to 37, 

 Table III., show typical results in regard to the specific gravity 

 of the corpuscles. Upon examining these results one finds that 



