DESCRIPTION OF THE PLATES. 
The letters throughout have the same signification : — a, trochal disc ; 
6, body ; c, tail of peduncle ; e?, mouth ; e, pharynx ; /, " yellow mass ;" 
gizzard ; 7i, " pancreatic sacs ;" ^, rectum ; k, anus ; Z, ovary ; 
water- vessels ; ganglion ; o, ciliated sac ; upper circlet of cilia ; p'^ 
lower circlet of cilia ; r, vacuolar thickenings. 
PLATE I. — Laciiiularia socialis. 
Fig. 
1. A single individual from the side. 
2. Lateral view of the trochal disc. 
3. Trochal disc from above. 
4. Aperture of the mouth — ciliated sac and ganglion. 
5. Animal retracted. 
6. Armature of the gizzard, viewed laterally. 
7. Termination of a water-vessel in the trochal disc. 
8. Water- vessel much magnified, showing the long flickering cilium. 
9. A portion of the ovary much magnified, showing the germinal vesicles 
with their spots scattered through its substance. 
10, 11. Stages in the growth of the ovum. 
12-18, Stages in the development of the embryo. 
19. Spermatozoon? 
PLATE II. 
20. A portion of the ovary undergoing the change into an ephippial ovum . 
21. 22. Ephippial ova, the latter having its contents divided into two 
portions. 
23. Ephippial ovum burst. 
24. Its contents. 
25. Muscular fibre — relaxed, a ; contracted, 5. 
Melicerta ringens. 
26. Viewed laterally. 
27. From the ganglionic side. 
28. From the mouth side. 
29. Extremity of the calcar, showing its apparent closure and the bundle 
of cilia. 
BracMonus pdlyacanthus. 
30. Viewed laterally. 
31. From the mouth side. 
32. From the ganglionic side. 
33. From above. 
Philodina, sp. ? 
34. Trochal disc from above. 
35. laterally, 
36. From the mouth side. 
37. From the ganglionic side. 
