623 
Diémyctylus. We hope soon to present a detailed description of these 
observations together with figures, and shall confine ourselves here 
to a brief statement of the general results. With the help of plane 
mirrors we were able to watch the rise and progress of the furrows 
over the whole surface of the living egg, thus avoiding the disad- 
vantages that arise if the position of the egg is changed. 
1. The first meridional furrow usually divides the egg into two 
approximately equivalent portions, but: 
(a) The first furrow may fall so far to one side of the mid 
line that one of the cells may be double the size of the 
other. 
2. The second meridional furrow forms at right angles to the 
first, but: 
(a) There are all gradations between this and highly acute 
angles. 
(b) The furrow may begin in the middle of the animal pole 
and extend over both halves simultaneously, or division of 
one half may quite outstrip that of the other. 
3. The third set of furrows is usually equatorial. 
(a) It may begin at either of the meridionals and extend in 
one direction around the egg, or in both directions simul- 
taneously, or appear in each quadrant without order. 
(b) It may begin at or near the upper pole, pass obliquely 
towards the lower pole and then curve towards the equator. 
In such a case the equatorial nature of the furrows is 
obscure. 
(c) The third set of furrows may be completely vertical in 
each of the four quadrants and pass from the upper pole 
to the lower, precisely like a true meridional. In this 
event an equatorial may or may not follow. 
(d) There are all possible variations of the third set of 
furrows between a true equatorial and a true vertical. 
4. The fourth set of furrows is less constant in position and 
regularity than any of the preceding. Each quadrant usually 
shows radical individual differences. In case the third set of 
furrows is irregular, the fourth is hopelessly intricate. 
In all the instances specified we have followed the further deve- 
lopment of the egg and assured ourselves of the formation of com- 
pletely normal embryos. 
It is clear from these facts that ectoblast and entoblast are not 
separated by the third set of furrows, that the early arrangement of 
41 
