EXPLANATION OF THE PLATES. 



PLATE XX. 



CORYNE JURABILIS, HaLOCIIARIS SPIRALIS, ClAVA 

 LEPTOSTYLA, RhIZOGETON FUSIFORMIS. 



[Figs. 11 to 16a, drawn from nature hy A. Sonrel; the others by 

 H. J. Clark.] 



Figs. 1 to 9. Coryne mirabilis Ag. 



Fit". 1. The end of a bydra stem rejuvenating, a the 

 liorn-like sheath ; li the stem of the hjdra ; i' the 

 expanded end of 6, attached to a. 200 diameters. 



Fig. 2. The stem of a hydra one half of an inch below 

 the tentacles, to show the numerous lasso-cells in the 

 outer wall (a), where they cannot possibly perform 

 any prehensile function, as they are covered by the 

 thick, horn-like sheath (c). h the inner wall ; d 

 chymiferous canal. 400 diameters. 



Fig. 3. Two young hydrie budding from opposite sides 

 of the stem. a outer, and b inner wall of the bud; 

 a' outer, and //' inner wall of the parent stem ; c 

 the horn-like sheath, which, at c\ covers the buds ; d 

 the chymiferous canal. 200 diameters. 



Fig. 4. A young hydra, with two incipient tentacles (t), 

 budding from an old indra stem (</). c horn-like 

 sheath of (/; rf' mouth of the young hydra. 100 diams. 



Fig. 5. A young hydra with four tentacles (t). Let- 

 ters as in fig. 4. 100 diameters. 



Fig. 6. A young hydra with eight tentacles, strongly 

 contracted. a outer, and b inner wall of the head; 

 a' outer, and 6' inner wall of the stem; c horn-like 

 sheath, which, at c', covers the head ; d digestive cavity ; 

 ( tentacles. 300 diameters. 



Fig. 7. Proboscis of a young medusa, not long free, to 

 show the replication of the walls. a the inner wall 

 folded outward; b the outer wall of the second pli- 

 cation; c base of the proboscis. 400 diameters. 



Fig. 8. A papillifbrm tentacle of the medusa of fig. 13, 



PI. XVn. «' the outer wall of large hyaline cells; 



6' inner wall ; (/' chymiferous cavity. 500 diameters. 



VOL. IV. a 



Fig. 9. End of the tentacle of a young medusa not long 

 free, a papillate bodies on the surface ; b groups of 

 lasso-cells; c outer wall. 400 diameters. 



Fig. 10. The hydra of Halocharis spiralis Ag., with its 

 Corynoid tentacles (t) developed from base to ajjex. 

 a outer, and b inner wall. 100 diameters. 



Fig. 10'<: The same as fig. 10, strongly contracted. 100 

 diameters. 



Fig. lOti. The upper part of fig. 10, more highly magni- 

 fied, a outer, and b inner wall of the body ; a' outer, 

 and b^ inner wall of the tentacle ; d digestive cavity ; 

 rf" mouth. 200 diameters. 



Fig. 10<^. A tentacle of fig. 10^, with the same letters. 

 200 diameters. 



Figs. 11 to 1.5. From a bunch of female medusae of 

 Clava leptostyla Ag. All magnified 200 diameters. 



Fig. 11. A medusa containing two eggs, a outer, and 

 b inner wall of the pedicel ; a' outer and only wall 

 of the disk ; ¥ eggs ; b* Purkinjean vesicle ; V end 

 of the inner wall ; d the proboscis; e cavity of d. 



Fig. 12. A medusa containing a segmenting, mulberry- 

 like mass (6'). 



Fig. 13. Medusa similar to that of fig. 12, but the seg- 

 menting mass, i', more minutely divided. 



Fig. 14. A medusa containing two or more very young, 

 irregularly spherical planulfe or young hydra; (JP). d 

 the proboscis. 



Fig. 15. A medusa whose planuhc (i') are elongate pyri- 

 form, and about to escape, e' chymiferous canal of the 

 pedicel; the other letters as in fig. 11. 



Fig. IG. A group of male medusas of Clava leptostyla At/. 

 A A have discharged their spermatic particles; B a 

 half-grown medusa ; the other two full-grown. a 

 wall of the medusa ; P spermatic mass ; d the probos- 

 cis. 200 diameters. 



Fig. IG*. Spermatic particles from fig. 16. 800 diameters. 



Figs. 1 7 to 23. Rhizogeton fusiformis Ag. ; the male ; all 

 but fig. 23 magnified 100 diameters. All the figures 

 have corresponding lettei's. a and a} the outer wall 



(1) 



