20 EMBRYOLOGICAL MONOGRAPHS. 



8-15. From AUmau, op. cil., PI. VIII. figs. 3, 7 ; PI. IX. figs. 3, 4 ; PL XI. fig. 9 ; PI. XVIII. fig. 4 ; 



PI. XX. fig. 4. 

 8, 9. Dicoryiie cmiferta. Aider. 



8. "The female locomotive, ciliated sporosae, shortly after its liberation," "as it appears when swimming." It 



is viewed at right angles to the plane of its two tentacles. 



9. Longitudinal section (optical) of a female sporosae made at right angles to the plane of the tentacles, and 



viewed under slight pressure. 



10. Aetinula of Tubularia indivisa., Linn. A zoold homologous to a free medusa, which is formed in small 



spherical sacs, hanging from an a.xis, dependent between the tentacles of the hydroid. 



"The aetinula, shortly after liberation. It is figured in the attitude as.sumed when moving from place to 

 place ; the mouth is turned to the surface over which the aetinula is moving, while some of the long 

 tentacles are bent in the same direction, and are employed as ambulatory organs." Allman. 



11. ClavatcUa proN/em, Hincks. An ambulatory larva, seen from the side, using its outstretched tentacles as 



walking organs. 



12. Young stage of a free medusa (gonophore) of Pcritjonimus. 



13. Young medusa of BouijainviUia, represented as it appears in motion. The bell walls are contracted, and the 



velum is pushed outward. 



14. An o\dev {^) Boii-nainvilHa, Hoating passively, with tentacles widely extended. Subsequent growth from a 



medusa in this condition into that of the adult takes place simply by an increase of the number of tenta- 

 cles and eye-spots in the bundles at the beil-rim, and an additional complication of the lips. 

 1.5. The same, older. 



16. Medusa of Oceania lanrjuida. From a sketch by Fewkes. 



The youngest stage of this gonophore. man. Manubrium, tn. Tentacle, tb. Chymiferous tube. 

 ubr. Umbrella, vcl. Velum. 



17-18. Zygodactyla Grocnlandka, A. Ag. From Fewkes, Studies of the Jelly-fishes of Narragansett Bay. Ball. 

 Mas. Comp. Zool. Vol. VIII., No. 8, PI. V. figs. 5, 6. 



17. Youngest known medusa of this genus, seen from the oral side of the disk. can. crc. Circular canal, mail. 



Manubrium, o cy. Otocyst. r. tb. Radial tube. r. tb'. Radial tube, which luis not yet extended to the 

 circular canal, ta. Tentacle. 



18. Same larva seen in profile, man. Manubrium. )•. lb. Radial tube. r. Ih'. Intermediate radial tube, which 



has not yet extended to the circular canal, o cy. Otocyst. to. Tentacle. The fully-grown medusa has a 

 very large number of radial chymiferous tubes, otocyst and tentacles. 



19. in/lia ornala. From A. Agassiz, np. cil.., fig. 274°. Young gonophore in which the tubes have just begun 



to bifurcate {r. tb.). The youngest form has four undivided tubes, alternating with four simple bundles of 

 nematocysts in the bell walls. 



20-22. Lizzia octopunctata. From Fewkes, Studies of the Jelly-fishes of NaiTagansett Bay. Bull Mt(s. 

 Comp. Zoo/., Vol. VIII., No. 8, PI. 1. figs. 1, 3, 6. 



20. Mother medusa, with buds in various conditions of growth forndng on the outer walls of the proboscis. 



mds.gm. Medusa buds. The lai-ger {mds. gm.) approximates in shape that of a medusa, lab. Lip. 

 ocl. Ocellus, or. Mo\ith. la.. Tentacle, ubr. Umbrella, vel. Velum. 



21, 22. Developed buds, with the form which they have when just escaped from the parent manubrium. 



21. Young medusa (oral view), cfiv. Bell cavity, ocl. Ocellus, ta. Tentacle, ubr. Umbrella, tc?. Velum. 



22. Side view of the last. man. Manubrium, at the base of wliich are buds of a third generation, r. tb. Radial 



tube. ubr. Umbrcdla. At the apex there is a canal which formerly afforded free communication between 

 the cavity of the manubrium of the parent and that of the bud. The bud, when it severs its connection 

 with the parent, has on the bell rim sixteen tentacles, consisting of four bundles of three tentacles eaeh, 

 and, alternating with these, four single tentacles. 



23. Young of ffalidyslus {Lacernariti?) From A. Agassiz, North American Acalepha;. Illustrated Catalogue 



Mus. Comp. Zool, No. 2, ji. 63. or. Mouth, ubr. Umbrella, tt. Base of attachment. 

 23°. A group of tentacles of the same, in different stage of growth. 



24''-24''. Schizocladium ramosum. From Allman, op. cit., p. I.'i2. 



24'. "Part of an adult colony, magnified about six diameters." o. A terminal part of a branch still invested by 

 a chitiuous perisarc. /3. The perisarc of this branch has been ruptured, while the contained canosarc 

 has protruded a little, and is visible at the extremity, f. The separation of a small body of coenosare from 



