96 ERNEST WARREN. 



Fig. 23. — X 150. Longitudinal section of gonophore with irregularly 

 sbaj)ed embryo, consisting of large Ijlastonieres with nuclei which stain 

 with difficulty, and apparently contain but little chromatin. The yolk 

 is concentrated towards the centre. 



Fig. 24. — X 150. Longitudinal section of gonophore with fully- 

 developed actinula. 



Fig. 25. — X 350. Egg-mass with ingested ova. It may be noticed 

 that the nuclei are not swollen as in Fig. 21 sn^ and sji^- 



Fig. 26. — X 300. Egg-mass with several nuclei, of wdiich n is one. 

 The centre of the mass is occupied by vacuolated protoplasm and yolk. 



Explanatory References. 

 a. Actinula. a. o. Abortive ovum. a. e. Amoeboid endoderni cells. 

 b. Truncated end of hydroid after the hydranth has di-opped off. b. ed. 

 Basal endoderni cells lying in contact with the mesoglea. b. ep. Basal 

 endodermal ej)ithelium. b. t. Basal or proximal tentacles, c. c. Covering 

 cells roofing over the endodermal canals, c. e. p. Central endoderni 

 passage, c. ch. Central channel, d. Diaphragm, dy. Dyaster. d. c. 

 Digestive cavity of hydranth. d. t. Distal tentacles, d. a. Digestive 

 cavity of actinula. ect. Ectoderm, end. Endoderm. e. c. Endodermal 

 canal, e. r. Endodermal ridge, e. rh. Ectoderm of liydrorhiza. c.a.ii. 

 Ectoderm filling abortive umlirella-cavity. e. u. Ectoderm of umbrella, 

 including both the germinal epithelium and the ectoderm lining the 

 umbrella-cavity. etZ,. Endoderni covering diaphragm on the under 

 surface, ed. Endoderm running up under the diaphragm, c. vi. Egg- 

 membrane, g-m. Granular masses of worked-up food material (?). 

 (/. e. 111. Generative epithelium fusing into an egg-mass. g. e. Germinal 

 epithelium, gl. Gland cell. gl. c. Glandular cell of endoderm. /. Endo- 

 dermal lobe. I. n. Large nematocyst. vies. Mesoglea. i. o. Ingested 

 ova. m^. The ordinary thin mesoglea of gonophore. iHj- The thick 

 mesoglea of abortive gonophore. n. Nucleus, o. Opening of umbrella 

 cavity to the exterior, o. e. c. Opening of endodermal canals into 

 hydranth. o. t. Adhering portion of oral or distal tentacles, p. Peri- 

 sarc. pr. Mass of worked-up food material in floor of hydranth. p7\. 

 Ditto in hydrocaulus. p. t. Proximal tentacles, p)- g- Perisarc groove. 

 pr. Proteid-like mass. ped. Peduncle. }). s. c. Perisarc-secreting cells. 

 r. Rootlet of liydrorhiza. r.ed. Reticular endoderni. r.f.g. Reserve 

 food-globules of endoderm. s. a. Swollen apex of rootlet, sp. The 

 modified sponge-tissue contiguous with hydrorhiza. s. c. Secreting 

 cells, s.c.p.g. Secreting cells of perisarc-groove. s.n. Small nemato- 

 cyst. s. m. Shrivelled manubrium, s. i;,. Swollen nucleus with nucle- 

 olus, s. 11^. Swollen nucleus with chromatin reticulum, t. Tuber-like 

 portion of hydrorhiza. v. s. Vertical septum, v. ed. Vesicidar endo- 

 derm. V. p. Vacuolated protoplasm, y. Yolk-mass. 



