MEM. M. C. Z., IX. No. 3.—ACALEPHS, POLYPS. 15 
12°. ‘‘The cone has increased in size, and the soft parts towards its proximal end have become retracted from the 
external chitinous walls.” 
124, “The internal structures have still further withdrawn themselves from the chitinous walls, with which they 
are now in contact only by a narrow proximal and a wider distal zone, between which they present the 
form of a tubular cylindrical column.” 
12°. “The distal zone of contact has become retracted from the summit of the eup-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 chitinous envelope has 
become the hydrotheca.” 
“The arrows in the figure indicate the direction of the currents in the somatic fluid.” Allman, p. 72. 
13°=135 148-14". Laomedea flexuosa. From Allman, op. cit. p. 86. 
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 spots.” 
13°. ‘*The germinal vesicle and spots have disappeared.” 
13°. ‘The vitellus 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.” 
14*-14*. Development of a planula from the morula. 
14s. ‘‘The segmentation-spheres have still further increased in number, while the most superficial have become 
arranged into a stratum distingnishable from the deeper portion of the ovum.” 
14". “‘The superticial stratum has become more distinct, and is now seen to be composed of long prismatic cells.” 
14. “The ovum has begun to elongate itself, and one end has become folded on the remainder.” 
14*. “The embryo, just after its escape in the form of a ciliated planula.” 
(Quotations from Allman, in 12-14.) 
15. Laomedea flexuosa. 16. Obelia geniculata. From Allman, op. cit. p. 48. 
15. Gonangium, with ova in its cavity in different conditions of development. apex. Opercular summit. 
bl sto. Blastostyle. mem. Membrane investing the contents of the gonangium. The ova appear in 
different stages of growth inside this membrane. 
16. Gonangium, with meduse in different conditions of growth, budding from the blastostyle. apex. Opercular 
summit. 61 sto. Blastostyle. mem. Membrane investing the budding meduse. . Calycle. The buds 
escape through an apical orifice. 
17, 18. Laomedea amphora, Ag. From Agassiz, op. cit. Vol. 1V., Pl. XXX. figs. 3, 5. 
17. Portion of a stem with attached hydranths and calycles. 
18. Magnified view of a single hydranth. cal. Hydrotheca. ga. Stomach. pr. Proboscidiform elevation. 
ta’. Tentacles. o. Ferule-like formation of the perisare. 
19-25. Eucope polystyla. From Kowalewsky, HABJIO TEHIA HAIb PASBIUTIEMB COELENTERATA., 
Pl. I. figs. 1, 3, 5, 8, 9, 10. 
19. Segmented ovum. 
20. Blastosphere, with the hypoblastic cells (1b.) budding into a central cavity. eb. Epiblast. 
21. An older stage, more elongated and with thicker epiblastic cells. 6. Hypoblastic cells. 
22, Planula with solid central mass of hypoblastic cells (2 6.), surrounded hy epiblast (ed. ). 
23, 24. Planula with a segmentation (gastric) cavity (ga. cav.). According to Kowalewsky the epiblast in an 
embryo of this age divides into two layers. The deeper of these layers is in our figure lettered hypo- 
blast (7 }.), as it is considered hypoblastic in origin. e6. Epiblast. hb. Hypoblast. 
25. Section of embryo showing the four infolding walls. (Compare with the four infolding walls dividing the 
young attached Seyphostoma of Chrysaora, and the young Actinozoan.) 
26-30. Tubularia larynx. From Koch, Vorliufige Mittheilungen iiber Colenteraten. Jenaisch. Zeitsch. 
Vol. VII., Pl. XXVI. figs. 12, 15, 16, 17, 19. ‘‘More or less schematic.’’) 
26. A Tubularian bud showing (¢ 4.) Epiblast, and 2b. Hypoblast. Between these an intermediate layer ? 
27. Section of an embryo (actinula ?), showing beginnings of tentacles on each side. 
28. Actinula. cav. Cavity. eb. Epiblast. 4. Hypoblast. ta. Tentacle. The axis of the tentacle is solid, 
and composed of hypoblastie cells. 
30. An embryo which has just attached itself. (Section.) 
