124 JAMES O. FOLEY. 



reconstruction period following the telophase in the dividing 

 spermatogonia. All traces of the chromatin nucleoli, as such, 

 have disappeared by the time of a mid-spireme formation. In 

 the late spireme the beaded appearance of the thread disappears 

 although its outlines remain rough up to and including the early 

 prophase chromosomes. The spireme breaks up into definite 

 chromosomes, twenty-two in number. 



By the time the spermatogonial growth period has reached its 

 height a great number of degenerating spermatogonia may be 

 seen throughout the testis. These degenerating spermatogonia, 

 and later, degenerating early spermatocytes, may be found in 

 lobules in considerable numbers up until the time the lobule 

 becomes filled with spermatozoa, but not later. 



The prophase chromosomes of the spermatogonial divisions in 

 Umbra are very long and thread like, and irregular in outline. 

 No definite equatorial plate seems to be formed. Agar ('n) 

 found a similar condition to exist in the spermatogonial cells 

 of Lepidosiren. Subsequent metaphases or late prophases of 

 these chromosomes show marked variation as to length, shape, 

 thickness, and regularity of outline. Fig. 5 shows an early 

 metaphase stage in which the chromosomes are all long and 

 curved and mainly in the shapes of V's and L's; they clearly 

 display differences in size, thickness, and shape. Still earlier, 

 however, no such marked condition is to be seen, for the chromo- 

 somes are then all approximately of the same size, length, and 

 thickness. 



Figures 5 to 13 and 56 to 60 show progressive condensation 

 changes in the chromosomes. These series of figures show that 

 a gradual contraction takes place in all the chromosomes until 

 a condition is reached like that shown in Figs. 12 and 13. Agar 

 ('12), working on Lepidosiren paradoxa, found a similar con- 

 densation taking place in its chromosomes, the chromosomes 

 contracting toward the apices of the Vs. Figs. 12 and 13 show 

 spermatogonial cells which exhibit this condition to a marked 

 degree. Such contraction phases can be easily demonstrated in 

 early spermatogonial cells because in this growth period such 

 cells are very large, and the multiplications which take place 

 are very slow. Later and smaller spermatogonial cells, in the 



