42 . EMBRYOLOGICAL MONOGRAPHS, 
PLATE XIL 
* : ? cd 
Development of Zoantuarta and Arcyonania. Figures from A. O. Kowatevsky, Erieny 
Jourpan, Wituetm Buscu, ALExanpEer AGassiz, Epwarp L. Mark and Caru Cuavs. ae 
an. po. Anal pore. 7g. mu’. Tongitudinal muscles of mesenteries. — 
bid. Blastoderm. _ mb. pa. Membrana propria. 
cam. Artificial chamber between ec. and en. ait. Mesenteries. " 
cil. Cilia. m nt. fil. Mesenterial filaments. 
d. Dorsum, and dorsal mesenteries. ms d. Mesoderm. ae 
dl. Dorso-lateral mesenteries. or. Mouth. 
dx. Dextral. or. ta. Oral tentacles. 
ec. Eetoderm. : phe. Pharynx. 
cn. Entoderm. Sue Sinistral. 
en’, Intermesenterial ridges of en. sg. cav. Segmentation cavity. 
gtt. ol. Oil globules. ta. Tentacle. 
lab. Oral lips. 0. Ventrum, and ventral mesenteries. 
ig. mu. Longitudinal muscles. vl. Ventro-lateral mesenteries. 
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1-9. Cerianthus membranaceus. 1-6, 8, 9, from A. O. Kowalevsky, Observations on the development of the _ 
Ccelenterata. From the Publications of the Imperial Society of Friends of Natural Sciences, Anthro- 
pology, and Ethnography. Moscow: Katkov. 1873. (Russian.) Pl. VI. 
1. Egg after the segmentation is completed.3,°. The blastoderm, of a single layer of uniform columnar cel ae 
embraces a comparatively large segmentation cavity. 
2. Stage showing the invagination of one half of the blastoderm into the other half. At the bottom of the sd 
cavity are seen fat globules (tt. ol.) which came out through the invaginated cells, en. A> 
3. A farther developed stage, already slightly elongated. 
4. The edges surrounding the mouth-opening have been infolded to form the beginning of the stomach, phe 
Nore. — This infolding affects principally only two opposing sides, whereby the cavity thus formed 
is bounded on two sides, as shown in this figure, by both layers (ec. and en.)of the infolded wall, whereas 
at the two remaining sides the infolded portion of the ectoderm isin immediate contact with the superfi-- 
cial layer, the entoderm not being involved in the folding. The upper part of the entodermie cavity is 
thus divided into two lateral pockets. Courpare fig. 9 fi 
5. A still more developed stage, in which four tentacles (/a.) have appeared. The rim or lip which surrounds — 
the mouth-opening is seen through the substance of a tentacle at 2a. 
6. A swimming larva of Cerianthus, which shows, beside the four tentacles, a pair of oral tentacles (or. ta), a oo 
pair of mesenterial filaments, and an indication of the so-called anal pore at the aboral end. ‘ 
. Longitudinal section of a larva of Cerianthus membranaceus. 39. From Etienne Jourdan, Recherches zoo- 
logiques et histologiques sur les Zoanthaires du Golfe de Marseille. Aun. sei. nat., sér. 6, zool., Tom. XG 
Art. no. 1. PI. XVI. fig. 121. 
8. Transverse section through the posterior end of the larva represented in fig. 5. The longitudinal muscles 
of the wall, lying on the outer margin of the membrana propria, are shown ent across at ly. mu. These 
are believe to have originated from the ectoderm. The cut ends of the longitudinal muscles on both 
sides the mesenteries are seen at 7g. mu. 
9. Transverse section through the upper end of the same larva. 
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10-15. Cerianthus? (Dianthea nobilis Busch). From Wilhelm Busch, Beobachtungen iiber Anatomie und Ent- 
wickelung einiger wirbellosen Seethiere. Berlin: A. Hirschwald, 1851. Taf. XVII. figs. 1, 2, 4, 5, 7, 8. 
10. Young larva, uniformly ciliate ; too opaque to show internal strneture. 
