348 
CRESSWELL SHEARER. 
then slowly melted, and after remaining melted long enough 
to penetrate the eggs is cooled again. The eggs in the 
meantime remain close together in a heap and can be after- 
wards cut all in one small block. On the whole I have 
obtained the most satisfactory results with the first method, 
i.e. of attaching the eggs to a bit of liver with albumen, 
tiresome as this operation is to perform. 
3. Fertilisation and Early Oogenesis. 
If an egg-capsule about twelve days old is examined under 
the low power of the microscope, it will usually be seen that 
the young worms within it are about to hatch. The females 
are distinguished by their size and the conspicuous red eye- 
spots. At this stage they are curled up, and if ready to 
hatch, are revolving slowly within the egg membrane. The 
males are not so conspicuous on account of their small size 
and their lack of any marked conspicuous anatomical 
feature. Gradually the movements of the female become 
more and more vigorous, until she finally frees herself from 
the egg membrane. At this moment she is usually joined by 
one of the males, which immediately attaches itself to her so 
closely that after a moment or two it can hardly be dis- 
tinguished. If it had not actually been seen to join her, it 
would be almost impossible to tell that the small dot on the 
side of the female was not merely a fold of the body-wall. 
If the male is then closely watched, it will be seen to contract 
strongly several times in succession, and this corresponds 
with the injection of the sperm. If the conditions for observ- 
ing the act of copulation are favourable, it is possible to see 
the sperms as they pass out of testis or vesiculae and down 
the short penis and lodge finally within the body-wall of the 
female. All this time the female is moving rapidly within 
the egg-capsule, and almost as fertilisation takes place 
usually succeeds in forcing its way out of the capsule. The 
moment after the male has contracted in the act of discharg- 
ing the sperm, it becomes detached and remains behind in 
