(10) 



EXPLANATION OF THE PLATES. 



Fig. 8. A minutely divided mass (ae). li A' as before. 

 Fig. 9. An ovary of Tiaropsis diademata, seen obliquely 



from above. o n" o* a' the median wall of the 



medusa; h ft' the innermost wall. 100 diameters. 

 Fig. 9*. A transverse, sectional view of fig. 9. Tlie 



letters as above. 

 Fig. 10. An incipient tentacle. a outer, and h inner 



wall of the bud ; a' outer, and U median wall of the 



disk ; c circular canal. 400 diameters. 

 Fig. 11. A young tentacle, a outer, and h inner wall; 



ft' the base. 400 diameters. 

 Fig. 12. An ocular coronet, seen obliquely from above. 



a outer, and h median wall of the edge of the disk ; 



a} outer wall of the tentacle ; a? outer wall of the 



coronet ; U inner wall of the coronet ; c the semicircle 



of refractive bodies ; d the boss-like edge of the disk ; 



e the pigment spot ; / circular canal. 400 diameters. 

 Fig. 13. The same as fig. 12, but seen strictly from 



above, so that the disk (Ji) partly overshadows it ; 



the same letters ; also y the innermost wall of the 



disk. 

 Fig. 14. The same as fig. 12, seen from below, with 



similar letters. 

 Fig. 1.5. An edgewise view of fig. 12, with similar 



letters. 



PLATE XXXII. 



Dynamena PDMiLA-Xamx. 



[Figs. 1, 4, and 4a, drawn by A. Sonrelj the rest by H. J. Clark.] 



Fig. 1. A hydrarium creeping over a sea-weed. Natural 

 size. 



Fig. 2. Two pairs of hydra calycles ; the hydrie of the 

 upper ones are omitted, a outer, and h inner wall ; 

 a' outer wall of the upper pair ; c c' base of the 

 hydra where it passes through the semi-partition (d) ; 

 m aperture of the calycle ; op operculum of an im- 

 mature hydra calycle ; p the proboscis ; t tentacles. 

 100 diameters. 



Fig. 3. A pair of hydrae, and the bases of two branches, 

 seen from the convex side, i the branch ; k a calycle 

 of the branch ; op as in fig. 2. 100 diameters. 



Fig. 4. A hydra emerging for the first time from its 

 calycle (h). Letters as in fig. 2. 100 diameters. 



Fig. 4». The same as fig. 4, just before emerging. 



Fig. 5. An oblique end-view of a young, reproductive 

 hydra. 125 diameters. 



Fig. 5*. The same as fig. 5, in profile, o, a} the outer 

 wall ; (/ e the inner wall ; c the calycle. 300 diam- 

 eters. 



Fig. 6. A pair of young hydra;. a a} a' the outer 

 wall ; b the fold of the horn-like sheath, at the base 

 of the calycles ; i' the sheath iu process of formation ; 

 c the exterior portion of the sheath ; d the inner 

 wall of the matured stem ; e e^ e' inner wall of the 

 young hydra ; e° inner wall of the growing stem ; 

 f ./ ' /■ tlie three divisions of the triple bud. 300 

 diameters. 



Fig. 6a. The top of the branch from which figure 6 

 was taken. 40 diameters. 



Fig. 7. A female hydromedusa. a the axis ; ff the 

 growing portion of the axis ; /( ramifications of the 

 axis ; ov the eggs. 60 diameters. 



Fig. 8. A mature male hydromedusa ; a' the outer, and 

 e the inner wall of the axis ; b the outer, and 6' 

 the inner wall of the medusa ; c the calycle ; </ the 

 terminal exjiansion of the axis; / the proboscis of the 

 medusa ; /' the base of i ; sp the spermatic mass. 

 100 diameters. 



Fig. 9. A mature female hydromedusa. Letters as in 

 fig. 8; also oo the eggs. 100 diameters. 



Fig. 10. A young hydromedusa. A the main stem ; 

 o} e h h'- c (J li as in figs. 7, 8, and 9. 80 diams. 



Fig. 10a. A gi'oup of hydromedusse. A the main stem; 

 BCD the three calycles; h the branches decurrent 

 from the axial, chymiferous canal ; i point of junction 

 of C and D ; j the axis. 60 diameters. 



Fig. 11, a. A spermatic particle from fig. 8. 500 

 diameters. b c diagrammic figures of a. 



Fig. 12. A sectional view of a pair of hydrae, and the 

 terminal development of the main stem, a outer, and 

 b the inner wall of the stem and the hydra ; a' the 

 the processes from a ; c the aperture of the semi- 

 partition (f/) ; g the chymiferous channel ; h the flat 

 end of the stem. 100 diameters. 



Fig. 13, a e. Cells from the outer wall of fig. 14". 

 500 diams. b c d f g h i diagrammic figures of a e. 



Fig. 14. Profile view of figs. 5 and 5*. a the hydrome- 

 dusa ; m the mouth of a hydra-calycle ; A the stem. 

 1 25 diameters. 



Fig. 14". A pair of hydra', just beginning to bud from 

 the main stem, a the outer, and d the inner wall ; 

 c the horn-like sheath ; e- the end of the inner wall of 

 the stem ; e <? the inner wall of the hydra;. 300 diams. 



Fig. 15. A hydra just before the tentacles develop. 

 The letters as in fig. 12; also m the chitinous sheath, 

 between the hydra and the main stem ; I the roof- 

 like end of the calycle. 300 diameters. 



Fig. 16. An egg removed from the medusa, like that 

 in fig. 9. A the yolk, 500 diameters ; B the egg, 



