MEM. M. C. Z., IX. No. 3. — ACALEI'liS, POLYPS. 



35 



PLATE X. 



Development of the CiENOPnORA, enntmued. Fiyures from Carl Cliun' and J. Walter Fewkes. 



A. adr. lb. 



anrA-aiii 

 C. cil. 

 cW. 



E. CA'l., ex. 2 



ex. I. tb. 



G. ga. 



(/a, en. 



ga. sell. 



ga. tb. 



gaw. 

 JI. hh. 



hh.,^hh'. 



hb\, hb\ 



I. i.T.lb. 



i.r.tb. 

 L. lb. 



l.mu. 

 M. riuj.w. 



" Ailradirvl " chj-mifiTous tube. Tlie 



aJraiUal tube passes to the .short rows 



of flappers. It arises from the iii- 



tcrracUal tube. 

 .< Auricles. 

 C'iliuin. 



Tuft of cilia before closure of otocyst. 

 External oiienings from the funnel, 



probably e.xci'etory. 

 E.xternal lateral tube bounding the 



lower rim of the body lobes (lb). 

 Stomach. 



Bifurcation of the stomach tube. 

 JIagengefassschenkel. 

 Stomach tube. 

 Appendage to the stomach. 

 Hypoblast. 



Large hypoblast cells. 

 Beginning of the chymiferous system 



of vessels. 

 Internal lateral tube. 

 Internal radial tube. 

 Body lobes. 

 Lateral muscles. 

 Median gelatinous prolongation near 



the otocyst. 



■mu. 

 mu.crc. 



N. M.-)l.' 



n c. 

 0. oaj. 



ol. 



or. 

 P. 2><'>'. O- 

 <S'. sell. 



s.gw. 



sph. 

 sph. tb. 

 T. ta. 

 tb.-tb.» 



X. X. 





0. 



Muscles. 



Muscles surrounding the stomach. 



Nerves. 



Nerve centre 



Otocyst. 



Otolith. 



Mouth. 



liadial canal before division. 



Tentacular cover. 



Gelatinous elevations on the side of 



the otocyst. 

 Funnel. 



Tubular region of the funnel. 

 Tentacle. 

 Cliymiferous tube extending to the 



tentacle. 

 Junction of three chymiferous tubes. 

 Line of the internal wall of the lobe 

 at the point where the chymiferous 

 tubes seem to cross it. 

 Junction of tubes at base of auricles. 

 Vibratilc flappers. 



Simple division of chymiferous tubes 

 without tentacle in genus Ocijroe. 



1-19. From Chun, op. cil., PL II. figs. 9, 10; PI. VII. figs. 1, 4, C, U; PI. VIII. fig. 4; PL IX. figs. 3, 



4, 8, 15, IG ; PL XII. 3, 4, 6, 7, 8, 11. 



1-10. Development of Chiaja {Eiicharis) muUieornis. 



1. Segmented ovum, showing the larger cells, "vitelline cells" within, surroundeil by smaller cells of epiblast. 



The opening through which the larger cells appear is a blastopore. 



2. Embryo in which the epiblastic cells have alnmst completely closed the opening {hip) seen in figure 1. The 



remains of this orifice apjiears as a long narrow slit. 



3. Optical .section of the gastrula. 



4. The gastral mouth now cjniiilctely closes, and the wall of the epiblast begins to infold to form the future 



mouth and stomach. 



Embryo in which this infolding has assumed considerable size, and in which, also, the tentacular promi- 

 nences (fa) have begun to form. An otocyst is already formed, while a single otolith is repj'eseutcd in Chun's 

 figure, which has not yet grown into the otocyst. The investing layer is the epibla.st. hb. Endodcrm, 

 hy])oblast. At the ]ioint mu. is the lieginning of the muscular layer which later becomes very prominent. 

 1). Vibratile row of flappers, cil'. Tufts of cilia. 



5. Still older larva in which the size of the layer between the outer thin epiblast and the larger cells, hypo- 



blast (A i*., hb.*), h.as increased greatly in size. In the latter the star-like muscular cells can be seen. 



