BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY. 
16. The same, but from a basal portion of a small branch: a, the cauline 
tube ; 6, the lateral communications between the cauline tube and the 
hydrothece, The specimen from which this figure was made has another 
cauline tube on the under surface of the branch, but as its outlines, 
like those of the orifices of the lateral communications, are exactly be- 
neath those upon the upper surface, they cannot very well be repre- 
sented. 
17 و و6‎ d. Represent a number of cross-sections of stems of O. conferta, 
taken from specimens having two cauline tubes. s, s, indicates the 
tubes in each, and A, A, the hydrothece. It will be observed that the 
hydrothece are always, and the cauline tubes never, in contact. 
. 18. Portion of the branch of the same. A lateral view showing the nature of 
the internal orifice of the ده‎ 
. 19. A lateral view of the same from Professor Allman’s type specimen. 
. 20. Portion of a branch of C. conferta from near the distal end ; from Pro- 
fessor Allman’s type specimen. 
PLATE IV. 
. 21. Obelia hyalina: a, main stem; b, branch; e, gonangium ; d, developing 
medusæ. 
. 22, Campanularia coronata : a, hydrocaulus ; b, branch ; c, hydrorhiza, 
23. One of the peculiar gonangia of Lafoéa convallaria : a, a, the two external 
orifices ; b, the point of attachment to the stem. 
- 24. Lafoéa robusta : five forms showing considerable specific variation, 
. 25. Lafota serrata. 
26,26 b. Sertularia complexa, ; view of upper surface of branch : a, a, orifices 
by which hydrothece communicate with stem or tube of the branch. 
. 27. The same ; lateral view : lettering as before. 
28, 28 b, Front and back views respectively of the same : b, the cut end of the 
stem. 
PLATE ۰ 
. 29. The proximal part of the main stem of Plumularia gracilis, showing the 
thick chitinous walls of the perisare and the transverse nodes. 
. 90. Part of the upper or distal portion of the same, with very oblique nodes. 
. 90 b. Lateral view of a hydrotheca of same. 
. 90 c. Lateral view of portion of a branch showing arrangement of internodes in 
the branches. 
. 91. Cladocarpus gracilis ; lateral view. 
. 915. The same ; front view. 
. 82, Lateral view of portion of a pinna of Nematophorus grandis. 
33. Front view of the same. 
. 94. Portion of main stem of the same: a, a, a, a, a, oval bodies with 
mesial nematophore openings ; b, b, b, cauline nematophores ; c, c, 6 €, 
internal orifices of the latter; d, d, external orifices of the cauline 
nematophores ; e, lateral view of a cauline nematophore. 
35. An enlarged view of a small part of a pinna of N. grandis, showing the 
contents of a mesial nematophore as they were preserved in alcohol, 
252 
Fig. 
Figs. 
Fig. 
