GERM-CELL HISTORY IN THE BROOK LAMPREY 



71 



gland. If in older larvae of this period, the number of cysts is 

 greater than the number of oocytes, the larva probably becomes 

 a male; if the number of growing oocytes is greater than the 

 number of cysts, it probably becomes a female. In younger 

 larvae of the period this cannot be a reliable criterion, for in 

 some cases oocytes do not apparently begin to form in great 

 numbers until the larvae are over 5 cm. long. Other larvae of 

 the same size show evidence of having formed a large number of 



TABLE 4 



Diagram showing the relative number of cysts and oocytes in various lamprey larvae 



during the period of sex differentiation 



oocytes in their early stages, but appear later to have formed 

 cysts only. Other larvae show about equal tendencies to form 

 oocytes and cysts during the whole intermediate period. 

 • The relative number of cj^sts and oocytes found in the various 

 larvae of this period may be represented in percentages from one 

 to a hundred as shown in the above table (table 4), which 

 should be compared with table 2 (page 12). 



The circles in the table represent ova, the small dots cysts. 

 The spaces between the vertical lines may represent individual 

 larvae, and the relative number of cysts and ova in the glands 



