TUE SIZE OF ORGANISMS 



189 



the protoplasm has been transformed into the contractile substance of 

 the flagellum. 



I have not been able to measure the volume of muscle cells in 

 Crepidula, but such measurements have been made by Eycleshymer^' 

 for the striated muscle cells of Necturus. From the measurements 

 given by Eycleshymer, I have calculated the nucleus-plasma ratio in 

 the usual manner, i. e., by determining the ratio of the nuclear volume 

 to the cell volume less the nuclear volume ; and I find that in the 7 mm. 

 and 8 mm. embryos this ratio is about 1 :11, whereas in the 23 cm. 

 adult it is about 1 :73. The increase of cell substance is therefore less 

 than seven times, instead of twenty or thirty times, that of the nucleus, 

 as he states. 



Eatio of Nucleab Volume to Cell Volume in Adult Individuals op 

 Crepidula plana 



Kindi of Cells 



Spermatocytes I 



Spermatocytes II 



Spermatids (chromatin con- 

 denied) 



Oocytes I (before yolk forma- 

 tion) 



Large ganglion cells (not in 

 eluding any outgrowlhg).. . 



Ectodermal epithelium (of 

 foot) 



Epithelium of mantle (near 

 anus) 



Inteitinal epithelium 



Gastric epithelium 



Branchial epithelium 



Liver cells (without secretion 

 products ) 



Liver cells (with secretion 

 products ) 



Oocytes I (before maturation 

 and with maximum quantity 

 of yolk) 



Maximum 



Diameter 



of Cell 



8 



7 



3 

 10 



17X17X23 

 6X 6X15 



5X 5X15 

 11X11X12 

 10X10X36 



7X 7X 9 



14X14X30 

 15X15X45 



150 



Nucleus- 

 Cell Ratio 



1: 1.37 

 1: 1.7 



1: 2.38 



1: 3.5 



1: 6.3 



1: 7.1 



1:10.3 

 1:11.8 

 1:12.4 

 1:12.3 



1:14.4 



1:88.6 



1:53 



It is important to note that Eycleshymer found that as the fibrillae 

 are progressively formed out of the protoplasm of the cell, the nuclei are 

 crowded out of the center of the cell toward its periphery; that the 

 nuclei become more densely chromatic, and especially so on the side of 

 the nucleus toward the fibrillae ; and that possibly the nuclei may disin- 

 tegrate and their chromatin go to form the dark bands of the striated 



"Eycleshymer, "The Cytoplasmic and Nuclear Changes in the Striated 

 Muscle Cells of Necturus," Am. Jour. Anut., 3, 1904. 

 * Nucleus shrunken and irregular in shape. 



