THE EFFECTS OF HYPERTONIC SuLETIONS. 
457 
figures. These frequently show very much more chromatin 
aggregated at one pole than at the other. 
Fig. 26 shows the nucleus of a 2-celled stage; it contains 
two minute vesicular bodies which are found in such nuclei in 
other batches of “ hypertonic ” eggs. 
In spite of the profound disorganisation of the mitotic 
figures in this series of eggs, it is remarkable that in all the 
2-celled stages examined, not a single case of irregular 
cleavage was observed. This is quite in accordance with the 
work of Paula Hertwig (6) on the effects of radium emana- 
tions on the eggs of Ascaris megalocephala. She has 
shown that eggs subjected to such treatment undergo chro- 
matic degenei’ation in all respects similar to these eggs which 
were treated with hypertonic solutions; the mitotic figures 
disappear, the individuality of the chromosomes is lost, and 
the chromatin becomes aggregated towards each pole in 
irregular masses. She finds, however, that the first cleavage 
is perfectly regular (cf. her figs. 1-12). 
The structures found in this series of eys^s are iuterestiii'r 
in two respects : (1) they partially explain why egg’s of 
Echinus acutus when fertilised by Echin us esculentus 
sperm develop normally, although considerable irregularities 
occur within their chromosome complexes ; (2) they appear to 
indicate that cleavage of the egg is not primarily dependent 
on the existence of the mitotic figure. The chromatin appears 
to segregate into two groups, and the egg divides normally 
without the existence of asters. As Paula Hertwig points out, 
cleavage appears to be a function of the cytoplasm, and is 
only indirectly controlled by the mitotic figure. 
Series D. : E. esculentus. — Eg’gs treated with 50 c.c. sea- 
water -|- 8 c.c. 2^ M. NaCl for 30 minutes. 
Very few mitotic figures were found and no very definite 
statements can be made. Figs. 27-29 show nuclear figures 
of these eggs. It tvould appear as though the stage at which 
the chromosomes become visible as distinct units within the 
nuclear membrane is considerably delayed, and in many cases 
is never reached ; owing, however, to the scarcity of good 
