EXPLANATION OF THE PLATES. 



(9) 



the scalloped part of the operclc; d' (P the puffs of d. 



470 diameters. 

 Fig. 10. The hydra of Clytia intermedia, g the stolon. 



40 diameters. 

 Fig. 11. A single hydra of fig. 10. c the semi-partition ; 



c' the top ring of the stem ; o' the calyele ; c= the 



teeth; t the tentacles. 100 diameters. 



PLATE XXX. 



L.\OMEDE.^ .\MPIIORA Ag. 



[Figs. 1, 2, 3, 4, 5, 8, 9, 10, 11, 12, 1.3, 14, drawn by A. Sonrel; tlie 

 others by H. J. Cl.irk.] 



Fig. 1. A group of young hydra, attached to a sea-weed. 



Natural size. 

 Fig. 2. A full-grown bunch of hydra. Natural size. 

 Fig. 3. A portion of a branch of a hydromedusarium. 



8 diameters. 

 Fig. 4. A hydra, seen from above. A B the tentacles 



alternately elevated and depressed. 40 diameters. 

 Fig. .'5. A hydra in profile. A B as in fig. 4 ; fi the 

 calyele; c^ the rings of the pedicel; g the intra- 

 ealycine a.-tis; pr proboscis. 100 diameters. 

 Fig. G. A hydra calyele. a the border, and b the 



aperture of the semi-partition. loo diameters. 

 Fig. 6". End view of fig. 6. 

 Fig. G\ The papillate margin of the semi-partition of 



fig. 6. 400 diameters. 

 Fig. 7. The base of a hydra calyele. a the papilla; 

 along the margin of c ; 6 aperture of c ; c the semi- 

 partition ; ci actinal prolongation of c; c'- abactinal 

 prolongation of c. 300 diameters. 

 Fig. 8. The terminal development of a branch. a b 

 the youngest portion ; c' the horn-like sheath ; g the 

 chymiferous channel. 100 diameters. 

 Fig. 9. A partially-tlevelopcd hydra, ab the head; g^ 

 the axis of the pedicel; g" processes from the outer 

 wall of g. 100 diameters. 

 Fig. 10. A nearly mature hydra, a outer, and b inner 

 wall of the head; c°- rings of the pedicel; g digestive 

 cavity. 100 diameters. 

 Fig. 11. A hydra a little older than fig. 10. (^ c' c* 

 the pedicel and branchlet; d the caly.x ; g^ the axis. 

 100 diameters. 

 Fig. 12. A hydra a little older than the last, a outer, 

 and b inner wall; c' the calyele; c' the terminal ring 

 of the pedicel; g the digestive cavity. 100 diams. 

 Fig. 13. Similar to fig. 12, but the head is retracted. 

 100 diameters. 

 VOL. IV. 1 



Fig. 14. Tlie pedicel of a hydra, to show the very prom- 

 inent rings {c"). 100 diameters. 



Fig. 1.5. A female hydromedusa. /3 outer, and y inner 

 wall of the axis ; ae the egg ; d the end of the axis ; 

 /(' the medusa;; k the calyele; k"- rings of the pedi- 

 cel. 100 diametei-s. 



Fig. IG. A medusa from fig. 15. ae the egg; /, the 

 discoid termination of the inner wall ; A' the disk : 

 Ir the pedicel ; h' the chymiferous cavity. 300 diams. 



Fig. 17. The inferior end of the axis of a male Inilro- 

 medusa. A-D the medusa;; /3 the outer, and y the 

 inner wall of the axis; ae the spermatic mass; A' 

 the disk of the medusa; ¥ the proboscis of the me 

 dusa. 300 diameters. 



Fig. 18. A male reproductive calyele. A B, the medusii- 

 emerging in one mass; /.■ the wall of the calyele. 

 CO diameters. 



PLATE XXXr. 



FlG8. 1-8, L.\OMEDEA AMPnOKA Ag.\ FiGS. 9-15. 

 TiAROPSIS DIADEM.\TA Ag. 



[Drawn by H.J. Clark.] 



Fig. 1, A. A spemiatic particle, from fig. 18, PI. 30. 



500 diameters. B a diagrammic figure. 

 Fig. 2. A medusa from a mature hydromedusa. at 

 the egg ; af outline of the egg, next the inner wall ; 

 /i the discoid termination of the inner wall {¥) ; /;' 

 the disk; /(' outer wall; A' inner wall; /(» digestive 

 cavity; p the Purkinjean vesicle. 400 diameters. 

 Fig. 2». The Purkinjean vesicle of fig. 2. 500 diameters. 

 Fig. 3, 3''. Views from two opposite sides of a segment- 

 ing egg. a a' o' the dividing furrow ; 6 e the two 

 halves of the segmenting mass. 300 diameters. 

 Fig. 3b. An end view of fig. 3a. 

 Fig. 4. A quadrated mass. a n' as in fig. 3 ; b <■ 



d e the four segments; f g the secondary furrow. 

 Fig. 5, 5". An unequally quadrated mass ; letters as in 



figs. 2 and 4. 

 Fig. G. A surface view of a mass, divided into eight 

 segments, b ¥ c c' the four segments nearest the 

 eye; h ¥ li- as before. 

 Fig. G». The same as fig. 6, by transmitted light, b // 

 c c" correspond to those in fig. 6 ; d d} e e^ the 

 four segments in the distance; h V h- as before. 

 Fig. 7. A mass divided into thirty-two segments (cr 



of ag). h /(' h" as before. 

 Fig. 7a. One of the segments of fig. 7, isolated. 



