No. 2.] THE DEVELOPMENT OF THE NEWT. 299 



by Schultze. They do not arise from the disintegration of the 

 nucleoli, but exist before the nucleoli begin to migrate centre- 

 wards (see Fig. 16, PI. XVI). To the consideration of these 

 important structures we must now turn. 



Chromatin threads or Chromosomes. — I have hitherto referred 

 to the filamentous chromatin as if it were in the form of isolated 

 and independent elements. I freely admit that no convincing 

 proof can be adduced to show that there actually exist distinct 

 individual chromosomes rather than a single looped and twisted 

 skein. I have found it impossible to determine this point, but 

 I am so far influenced by the appearances observed in my sections 

 as to incline to the belief that the filamentous chromatin is in 

 the form of detached threads rather than in one continuous coil. 

 I shall accordingly use the term "chromosomes," premising, 

 however, that I do so rather for the sake of convenience than 

 for any strong belief in its absolute accordance with the facts. 



In sections through young eggs the chromosomes present the 

 appearance shown in Figs. 4 and 14. They are strings of co- 

 hering granules of varying dimensions, and in the youngest eggs 

 these granules are indistinguishable from the small nucleoli. 

 I have sometimes found threads somewhat resembling those 

 figured by Flemming ('82) in Siredon (p. 134) though his figure 

 of the egg of Rana (Fig. "jZ, PI. V) is much closer to the usual 

 appearance in the Q.g^ of the newt. Leydig ('88) has given for 

 Triton (Fig. 93, PI. XV) a representation very much like what 

 I have observed in Diemyctylus except in the disposition of the 

 threads. I have never seen chromosomes of the curious fila- 

 mentous structure found by Riickert ('92) in the Selachian Qg^ ; 

 the chomosomes of Diemyctylus are always of a loosely granular 

 texture. I have also never observed any association of the 

 chromosomes — if such they be — in pairs in the highly sug- 

 gestive manner figured by Kastschenko ('90) and Riickert ('92) 

 in the Selachian ^gg. 



The most striking difference between the chromosomes of 

 the stage shown in Fig. 4 and those of Fig. 16 is in the relative 

 susceptibility to stain. The young chromosomes stain compar- 

 atively readily and are in consequence easily detected. They 

 subsequently appear to undergo a gradual change in their 



