GERM CELLS OF ANURANS 265 
Maturation cycle of second-year larvae and formation of functional 
spermatozoa 
INIuch that should more properly have been discussed in this 
section has been referred to here and there earlier in this paper 
in order to clear up certain sources of confusion which might arise. 
The second-year larval sexual cycle differs from that of the 
first year in two ways : 1) The germ cells of the second maturation 
cycle are considerably smaller, the tetrads are consequently much 
smaller than those of the first maturation cycle, and have less the 
appearance of rings than of dumbbell-shaped bodies when at- 
tached to the first maturation spindle ; 2) mature spermatozoa are 
produced, there is little cell degeneration, but few polyasters 
occur, and hence few cases of fragmentation of the centrosome. 
All maturation divisions are normal. It is ob"\dous that there is 
a vast difference between the first and second maturation cycles 
of the male larvae; the first is aberrant, the second normal; one 
culminates in degeneration, the other in the production of func- 
tional male sex cells. 
The smaller size of the germ cells of second-year larvae is not 
difficult to explain. During the period of the first sexual ripening 
practically all of the germ cells in the gonads are affected, and 
consequently destined to degenerate and disappear. There are, 
however, a few primary spermatogonia with polymorphic nuclei, 
lineal descendants of the primordial germ cells, scattered here 
and there through the gonad, which fail to undergo the preco- 
cious maturation cycle. These cells are generally, though not 
always, found near the sex cord region. In the interval be- 
tween the first and second larval sexual cycles these cells appar- 
ently divide rapidly and spread through the gonads. It is 
probably the repeated division of these cells, and thek prog- 
eny that brings about the marked reduction in cell size, so 
noticeable at the second maturation cycle. The proliferation of 
germ cells is so extraordinarily rapid in the gonads of tadpoles 
just about to metamorphose that the cellular size becomes re- 
duced to a size scarcely larger than that characteristic of the 
larger stroma or peritoneal cells. Indeed, conditions are such in 
