MEM. M. C. Z., IX. No. 3.— ACALEPHS, POLYPS. 47 
10. A young polyp perfectly developed, having two cycles of tentacles. At the base the wall (¢ dic.) limiting the 
cup of the young polyp has already become very evident. 
11. The internal (entoderm) and external (ectoderm) layers are sharply marked. The elongated calcareous 
nodules indicate the points of origin of the septa. The three centres of deposit for each septum are 
located not in the external but in the internal (entodermic) layer. (Compare Koch's results, below, 
figs. 18-28.) 
12-15. Balanophyllia regia. From I. Jourdan, Recherehes zoologiques et histologiques sur les Zoanthaires du 
Golfe de Marseille. Aun. sci. nat., sér. 6, zool., Tom. X., Art.no.1. Pl. XVII. figs. 123, 124, 126, 127. 
12. Vermiform larva. }. 
13. A more advanced larva. }. 
14. Longitudinal section of a larva of the same stage as the preceding. 
15. Transverse section of a larva having six mesenterial plates. is d. The mesoderm in process of formation. 4°. 
16. Nore. — Figures 16 and 45 have been transposed by the lithographer. For the explanation of figure 16 see 
below. 
45, 17. Astrea (sp.2).. From A. O. Kowalevsky, Observations on the development of the Ccelenterata. From 
the Publications of the Imperial Society of Friends of Natural Sciences, Anthropology, and Ethnography. 
Moscow: 1873. (Russian.) Plate V. figs. 15, 17. 
45. Longitudinal section of the large, ciliated, brick-red larva. The central mass (vf.), evidently derived from 
cells, is now composed only of nuclei (z/.) and oil globules (gé#. o7.). The entoderm (en.) of the present 
stage forms only @ part of the many-layered entoderm of the fully developed polyp, the balance being de- 
rived from this central mass. 
Nore. — The dotted line from en should not have been carried as far as the central mass, but should 
have ended in the layer of columnar cells separating the ectoderm from the central mass. 
17. View of the larva from the oral end after it has become attached and flattened. ¢a!. The rudiment of a 
tentacle. The radial or intermesenterial chambers (7. cam.) appear as transparent cavities. 
Nore. — The central ends of the mesenteries bounding all the chambers except two are grouped in 
pairs, and in sucha way as to make the whole appear symmetrically divided by the line 7. That this line 
cannot, however, represent the projection of the plane of bilateral symmetry, is very evident from the 
studies of other observers. , 
18=28. Asferoides calycularis. From G. von Koch, Ueber die Entwicklung des Kalkskeletes von Asteroides caly- 
cularis und dessen morphologischer Bedeutung. Mittheilungen aus der Zoologischen Station zu Neapel, 
Bd. Til. 1882." Taf. XX., XXI- 
18. Somewhat more than one-half of a radial section of a young larva, killed the last of June, which had at- 
tached itself to cork (@). The first trace of the skeleton lies between ectoderm and cork in the form of 
small, more or less fused, calcareous concrements, ex. The section along the floor passes longitudinally 
through the entodermie thickening (ex!.) corresponding to the place subsequently occupied by the calca- 
reous septa (compare figs. 19 and 20, en!., sep.). 4°. 
19. Portion of a section from the same individual, parallel to the preceding section, but distant from the centre. 
Three mesenteries (m xt.) and two of the entodermic thickenings (en/.) are cut transversely. The begin- 
ning of the skeleton (cz.) is also to be seen below the ectoderm. 4°. 
20. Portion of a section similar to the preceding, through an older individual. One mesentery with a median 
layer of connective substance (mesoderm, msd.), flanked on either side by entoderm, is cut across, as are 
also two calcareous septa (sep.), continuous with the floor-skeleton. 4°. 
21. Marginal portion of a section from an individual killed in the middle of July. To shew the formation of 
the epitheca (ex.). 23°. 
22. A small portion of the base from the section shown in fig. 18, more highly magnified. The entoderm is 
vacuolated and contains nuclei. The mesodermic connective tissue is scarcely discernible (not well repro- 
duced in the lithograph). The ectodermie cells are nucleated and have sharp contours, especially at their 
free ends. The calcareous coneretions (ex.) are very small spheroids and double spheroids which lie between 
the free ends of the ectodermie cells and the cork. 
23. A portion of the preceding still more magnified, and giving a better idea of the form of the concretions and 
their relations to individual cells. 
24. The cells of the ectoderm from another part of the same section, together with a calcareous concretion. 
25. A stage somewhat older than that (compare figure 8) in which the septa remain separate. The latter have 
acquired by their lateral outgrowths a complicated form. A portion of them have fused with each other at 
the periphery to form the first trace of the mural layer (mwr.); in the centre also several have joined their 
fellows. A narrow rim of epitheea (e //ic.) is already formed, but remains distinct from the mural layer. 
