DESCRIPTION OF THE PLATES. 427 



PLATE IIL 



Fig. 1. A diagram intended to exhibit the structure of an Actinia, 

 but which must not be taken as strictly accurate, a is the 

 base, h the disc, c the tentacles, d the mouth, e the stomach, 

 / g and k the septa dividing the cavity into chambers, on 

 the free surface of which are the grape-like masses of ovary, 

 and in front of the ovary the convoluted bands. (Copied 

 from Shai'jiey. ) 



... 2. Kepresents a section of the Actinia as seen in reality. The 

 convoluted bands are seen covering the ovary, and tennin- 

 ating on the inner wall of the stomach. (Copied from 

 M. Hollard.) 



... 3. A magnified view of one convoluted band and ovary, with the 

 mesentery between them, as they appear when unfolded on 

 the glass slide, previous to examination under the micro- 

 scope. (M. Hollard.) 



... 4. Three rA/-mrf-cay;s«/es from an Actinia, greatly magnified ; one 

 with the thread still inside, the other two after the ejection, 



... 5. Vertical section of the Retina of a Perch, showing the relative 

 positions of the pigment layer, the rods and cones, the gran- 

 ules, fibres, and cells. (Copied from H. Miiller.) 



PLATE IV. 



Fig. 1. Camioanularia. — The figure to the right is of the natural size ; 

 that to the left is a branch greatly magnified. The Polype 

 is seen, flower-like, expanding itself at the summit. An 

 ovarian capsule, to the right, contains Medusae in various 

 stages of development. ((Jopied from Van Beneden.) 



... 2. Plurmilaria myriophyllum, natural size. Five of the branches 

 are seen developed into ovarian capsules. 



... 3. Kepresents the spontaneous subdivision of one worm into two. 

 The head of the second worm is seen formed at the segment 

 where the tail ought to be. (Copied from Milne Edwards. ) 



PLATE V. 



Fig. 1. Lamproglena pulchella, one of the crustacean Epizoa, greatly 

 magnified, and seen from below. The figure is copied from 

 Nordmann, with the addition of the ovisacs, not represented 

 in his plate, but which Burmeister, whose copy I possess, 

 has drawn in pencil. The Lamproglena is, found in the gills 

 of a ^sh.{Ci/prim(s Jeses). 

 ... 2. Sagitta Mariana greatly magnified ; natural size quarter of an 

 inch. I believe this to be a new species, and I have named 



