MEM. M. C. Z., IX. No. 3. — ACALEPHS, POLYPS. 15 



12". "The cone has increased in size, ami the soft parts towards its proximal end have become retracted from the 



external chitinous walls." 

 12*. "The internal structures have still further withdrawn themselves from the chitinous walls, with which they 



are now in contact only liy a narrow proximal and a wider distal zone, between which they jncsent the 



form of a tubular cylindrical column." 

 12". "The distal zone of contact has become retracted from the sunnnit of the cup-like envelope of chitine, 



tentacles have begun to sprout from its circumference, and a hypostome has risen from its centre. The 



leading features of the completely-formed hydranth are thus established, and its cliitinous envelope has 



become the hydrotheca." 



"The arrows in the figure indicate the direction of the currents in the somatic fluid." Allman, p. 72. 



13''-1.3', l-l^-H'. Laomcdca flcxuosa. From Alhnan, op. cil. p. S6. 

 13°-13''. Development of the morula from the ovum. 



13". " Young ovum in the gonophore previously to the disappearance of the germinal vesicle ; the germinal vesicle 



is here seen to contain several germinal rpots." 

 13'. " The germinal vesicle and spots have disappeared." 

 13°. "The vitelhis has become cleft into two segment spheres." 

 13''. "The ovum after a .second cleavage." 



13". "The segmentation-spheres have become numerous, and many of them now show a distinct nucleus." 

 13'. "The segmentation-spheres have greatly increased in number, and a nucleus can now be detected in each of 



them." 



1-15-14'. Development of a planula from the morula. 



14'. " The segmentation-spheres have still further increased in number, wliile the most superficial have become 



arranged into a stratum distinguishable from the deeper portion of the ovum." 

 H*. "The superficial .stratum has become more distinct, and is now seen to be composed of long prismatic cells." 

 H'. "The ovum Ii.as begun to elongate itself, and one end has become folded on the remainder." 

 H'. "The embryo, just alter its escape in the form of a ciliated planula." 



(Quotations from Allman, in 12-14.) 



15. Laomcdca Jlcxuosa. 10. Obclla rjeniculata. From AUman, np. cit. p. 43. 



15. Gonangium, with ova in its cavity in different conditions of development, npcx. Opercular summit. 



blslo. Bhistostyle. mem. Memlu'ane investing the contents of the gonangium. The ova appear in 



different stages of growth inside this membrane. 

 IC. Gonangium, with medusa; in different conditions of growth, budding from the blastostyle. apex. Oiiercular 



summit, b! s/o. Blastostyle. mem. Membrane investing the budding mediisoe. 7. Calycle. The buds 



escape through an apical orifice. 



17, IS. Laomcdca amphora, Ag. From Agassiz, op. cit. Vol. IV., PI. XXX. figs. 3, 5. 



17. Portion of a stem with attached hydrantlis and calycles. 



18. M.agnified view of a single liydrauth. cnl. Hydrotheca. ga. Stomach, pr. Proboscidiform elevation. 



i a'. Tentacles. <r. Ferule-like formation of the perisarc. 



19-25. Eiicojycpolystyla. From KoKa\e\yiiky,HABJV);[EmR RAJlTi PAGBnTIEMl COELENTEKATA., 



PI. I. figs. 1, 3, 5, 8, 9, 10. 



19. Segmented ovum. 



20. Blastosphere, with the hypoblastic cells {hb.) budding into a central cavity, eh. Epiblast. 



21. An older stage, more elongated and with thicker epiblastic cells, h b. Hypoblastic cells. 



22. Plauula with .solid ceutr.al mass of hypoblastic cells (/t 6.), surrounded liy epiblast (c b. ). 



23. 24. Planula with a segmentation (gastrii') cavity (rja. cav.). According to Kowalewsky the epibl.ast in an 



embryo of this age divides into two layers. The deeper of tliese layers is in our figure lettercil liypo- 

 blast (/i /<.), as it is considered hypoblastic in origin, eb. Epiblast. hb. Hypoblast. 



25. Section of embryo showing the four infolding walls. (Compare with tlie four infolding walls dividing the 



young attached Scyphostoma of Chrysaora, and the young Actinozoan.) 



26-30. Tubularia !anjn.r. From Koch, Vorliiufige Mittheilungen iiber Ciilenteraten. Jcnnisch. Zeitsch. 

 Vol VII., PI. XXVI. figs. 12, 15, 16, 17, 19. "More or less schematic") 



26. k Tubulari.an bud showing {rb.) Epiblast, and hb. Hypoblast. Between these an intermediate layer ? 



27. Section of an embryo (actiuula ?), showing beginnings of tentacles on eacli side. 



28. Actinula. cav. Cavity, eh. Epiblast. hb. Hypoblast, ta. Tentacle. The axis of the tent.acle is solid, 



and composed of liypoblastic cidls. 

 30. An embryo which has just attached itself. (Section.) 



