found in the Northumberland Lakes. 289 



Figs. 3, 4. Two much-enlarged views of the same before development of 

 the sperm- vesicles. 



Fig. 5. Two highly magnified views of the terminal portion of the 

 tentacle, exhibiting nodular enlargements, a, and terminal bulb 

 or nodule, b. 



Fig. 6. Egg after attachment to some foreign body much magnified, ex- 

 hibiting chorion : a, a, a, a few of the mucus-globules contained in 

 vesicles adliering to the egg. 



Fig. 7. A few of the same vesicles containing mucus-globules more highly 

 magnified. 



Plate VII. 



Fig. 1. Hydra much enlarged, exhibiting development of ova: a, basal 

 portion of tentacles ; b, mouth ; c, c, sperm-vesicles ; d', ovum 

 considerably advanced ; d, ovum just before it bursts through its 

 envelope, e. 



Fig. 2. Much-enlarged view of egg as it appears immediately after it has 

 burst the envelope : a, egg ; b, b, margins of envelope ; c, c, por- 

 tions of the animal. 



Mg. 3. A portion of Hydra much magnified, exhibiting the egg when ready 

 to separate from parent : a, portion of the animal ; b, egg ; c, c, 

 mucus-globules as they at first appear ; d, pedicle attaching egg 

 to parent; e, e, contracted margins of envelope. 



Fig. 4. Enlarged view of Hydra much contracted with egg attached, ex- 

 hibiting anal orifice : a, mouth ; b, anal orifice as seen through the 

 substance of the adhesive disc ; c, faeces passing out of same ; c?, 

 sperm-vesicle ; e, egg with undulated margins ; /, pedicle attaching 

 same to parent ; g, contracted margin of envelope. 



Fig. 5. Sperm-vesicle much enlarged of the Hydra from the Northumber- 

 land lakes : a, gland-like body within the base of same ; b, apex of 

 same containing spermatozoa ; c, c, a portion of surface of animal. 



Fig. 6. Sperm-vesicle much enlarged of H. viridis : a, gland-like body 

 within base of vesicle ; b, apex of same containing spermatozoa ; 

 c, c, surface of animal. 



Fig. 7- Much -enlarged view of portion of tentacle of the flesh-coloured 

 Hydra as seen in the compressor, exhibiting captor organs and 

 organs of touch imbedded in the nodular enlargements : a, organs 

 of touch ; b, captor organs. 



Fig. 8. Two of the organs of touch greatly magnified, exhibiting inner and 

 outer vesicles and cilium. 



Fig. 9. Greatly enlarged view of retracted captor organ : a, outer vesicle ; 

 b, aiTow-head with barbs depressed; c, membranous stalk of 

 same ; d, inner or lining membrane doubled down upon itself. 



Fig. 10. Captor organ exserted : a, outer vesicle ; b, inner or lining mem- 

 brane ; c, membranous stalk supporting arrow-head with the 

 three barbs, c', elevated ; d, filament passing out of the pointed 

 extremity of arrow-head. 



Fig. 11. Two enlarged views of elliptical sacs with filaments supposed to 

 be poison-organs cast from captor organ. 



Fig. 12. Two of the spermatozoa highly magnified from s])erm-vesicle of 

 flesh-coloured Hydra. 



Ann. ^Ma^.N. Hist. Ser. 2. Vol, v. 19 



