252 BULLETIN OF THE MUSEUM OF COMrARATIVE ZOOLOGY. 



Fig. 16. The same, but from a basal portion of a small branch : a, the cauline 

 tube ; b, the lateral communications between the cauline tube and the 

 hydrotheca;. The specimen from which this figure was made lias 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. 



Figs. 17 i, c, d. Eepresent a number of cross-sections of stems of C. conferta, 

 taken from specimens having two cauline tubes, s, s, indicates the 

 tubes in each, and /(, h, the hydrothecfe. It will be observed that the 

 hydrothecpe are always, and the cauline tubes never, in contact. 



Fig. 18. Portion of the branch of the same. A lateral view showing the nature of 

 the internal orifice of the hydrothece. 



Fig. 19. A lateral view of the same from Professor Allman's tj'pe specimen. 



Fig. 20. Portion of a branch of C. confcrta from near the distal end ; from Pro- 

 fessor Allman's type specimen. 



PLATE IV. 



Fig. 21. Ohclia, hyalina: a, main stem ; h, branch; c, gonangium ; d, developing 



medusae. 

 Fig. 22. Campanularia coronata : a, hydrocaulus ; h, branch ; c, hydrorhiza. 

 Fig. 23. One of the peculiar gonangia of Lafoea convallaria : a, a, the two external 



orifices ; b, the point of attachment to the stem. 

 Fig. 24. Lafoea robusta : five forms sliowing considerable specific variation. 

 Fig. 25. Lafoea scrrala. 

 Figs. 26, 26 b. Scrtularia complcxa ; view of upper surface of branch : a, a, orifices 



by which hydrothecte communicate with stem or tube of the branch. 

 Fig. 27. The same ; lateral view : lettering as before. 

 Figs. 28, 28 b. Front and back views respectively of the same : b, the cut end of the 



stem. 



PLATE V. 



Fig. 29. The proximal part of the main stem of Plumularia gracilis, showing the 

 thick chitinous walls of tlie pcrisarc and the transverse nodes. 



Fig. 30. Part of the upper or distal portion of the same, with very oblique nodes. 



Fig. 30 b. Lateral view of a hydrotheca of same. 



Fig. 30 c. Lateral view of portion of a branch .showing aiTangement of intemodes in 

 the brandies. 



Fig. 31. CI adocar pus gracilis ; lateral view. 



Fig. 31 b. The same ; front view. 



Fig. 32. Lateral view of portion of a pinna of Nematophoms grandis. 



Fig. 33. Front view of the same. 



Fig. 34. Portion of main stem of the same : a, a, a, a, a, oval bodies with 

 mesial ncmatophore openings ; b, b, b, cauline nematophorcs ; c, c, c, c, 

 internal orifices of the latter ; d, d, external orifices of the cauline 

 nematophorcs ; e, lateral view of a cauline ncmatophore. 



Fig. 35. An enlarged view of a small part of a pinna of N. grandis, showing the 

 contents of a mesial ncmatophore as they were preserved in alcohol. 



