318 
MR. WILSON ON THE STRUCTURE .AND DEVELOPMENT OF 
f. The three labial palpi. The row of organs within the palpi are the 
maxillae whieh border the mouth and pharynx. 
g. Parts entering into the structure of the pharynx. 
h. The boundary lines of the collar. 
i. i. The first pair of thoracic plates. 
k, k. The first segments of the anterior pair of legs. 
Fig. 10 . The head, viewed upon its superior surface. 
The letters of reference to k are the same as in the preceding figure. 
l, The flask-shaped cephalic organ ; at the apex of this organ the con- 
vexities of the labeal palpi are seen. 
m, The eyeball, surrounded by its orbit, n. The thoracic carapax. 
o. The pointed termination of the flask-shaped organ. 
p, p. The oval bodies between which it is received, and to which part of 
the retractor muscle of the head is attached. 
PLATE XVI. 
Fig. 11 . A small mass of ovum-corpuscles ? These corpuscles measured 2^00 of an 
inch ; they are not drawn to a scale. 
Fig. 12 . Ovum-corpuscles increased in growth and containing numerous cells. This 
figure, like the preceding, is not drawn to a scale. 
Fig. 13. Three ova, showing progressive growth. The measurements of these ova 
were - 0 V 0 , sh and tto of an inch. 
Fig. 14. An ovum measuring of an inch in length. 
Fig. 15. An ovum measuring yyo °f an inch. 
Figs. 16, 1 7- Ova measuring of an inch in length. 
Fig. 18. An ovum elongated in figure, and measuring 3 X 0 of an inch. 
Fig. 19. An ovum which has assumed the form of the next stage of development of 
the Entozoon. 
The whole of the ova here represented exhibit structural modifications, having 
reference to development. This is particularly evident in figs. 16 and 17 . 
Fig. 20. Embryonic form of the long variety of the Entozoon ; fig. 19 exhibits a trans- 
ition to this form. The figure measured °f an inch in length. 
Fig. 21. An embryonic form, in a different position to the preceding. The specimen 
measured xihr °f an inch i n length. 
Fig. 22. An embryonic form in a different view. Length of an inch. 
Fig. 23. The largest embryo I have observed-. It measured in length. 
Fig. 24. An embryo upon the sides of which three pairs of legs are in progress of 
development. This is the first gradation in the six-legged stage of the 
long variety. The specimen measured xjo of an inch in length. 
Fig. 25. An animal more advanced in growth, and enclosed in exuviae. This speci- 
