THE EFFECTS OF HYPERTOXIC SOLHTIOXS. 
451 
vesicle similai- to those to be described later for other series of 
effSTs, while fiff. 2 shows a somewhat later stao’e in which tliere- 
is a small rounded mass of chromatin lying within the nucleus.. 
Later stages of these eggs, however, show a certain amount 
of abnormality. Irregular cleavage is not uncommon, and in 
some mitotic figures the chromosomes become scattered 
irregularly on the spindle (figs. 3 and 4). Fig. 5 shows a 
polyspermic egg ; this also is a fairly common occurrence in 
this batch of eg'o-s. 
Apparently the effect of the weak hypertonic solution is 
not sufiicient to affect the nuclear elements until later stages- 
than the first segmentation division. 
Series B. — Eggs treated with 50 c.c. sea-water + 6 c.c. 
5/2 M. XaCl for half an hour. 
Preparations of these eggs show that the effect of the 
hypertonic solution is (1) to induce polyspermy, and the pro- 
duction of tripolar and tetrapolar spindles, and (2) to produce 
abnormal chromatic bodies within the nucleus. The extra 
sperms are apparently derived from those which become 
attached to the fertilisation membrane which is extruded 
after the entrance of one spermatozoon. Figs. 6 a and 6 b 
sho\v the male and female pronuclei of one egg ; within the 
female nucleus is seen two very conspicuous bodies which will 
be referred to in this paper as “vesicles.” Tliese bodies are 
usually round or oval in outline, and stain progressively 
lighter from the periphery to the centre. In the male nucleus 
are seen four similar thonofh verv much smaller bodies. 
O k 
Fig. 7 shows the fusion of an accessory sperm nucleus with a 
zygote nucleus ; within the latter there can be counted over 
thirty definite chromosomes, while in the former there are 
about half this number.^ IVithin the larger nucleus ai*e seen 
one very large vesicle and four smaller ones, while within the 
accessory nucleus are also two small vesicles. 
These large vesicles ai-e characteristic of the female pro- 
nucleus, and must be derived fi'om the female element, 
' The somatic number of chromosomes for both Echinus escu- 
lent us audE. acutus is 38. 
