11-4 PROCEEDINGS OF THE ACADEMY OF [1889.. 



breadth. The individual polyps in the preserved condition measure 

 1-2 cm. in height, and in breadth at the upper end 05, cm. the 

 lower portion and stolons measuring about 0" 25 cm. All are strongly 

 contracted, a small depression being the only indication of where 

 the entrance into the interior is situated. The color, according to 

 the inclosed label, was "spinach-green," but this must be taken as 

 applying only to the upper part of the column, the lower part and the 

 stolons being brown or sand colored. The disc was " apple-green " and 

 the tentacles green. 



The column upon the outside is covered by a cuticle, in which 

 are sparingly imbedded foreign bodies. The ectoderm is separated 

 from the cuticle by a layer of mesogloea, and consists of cells ar- 

 ranged in groups separated by partitions of mesogloea, but not show- 

 ing the degeneration which occurs in Z. sociatus. The mesogloea is 

 comparatively thick, and consists of a homogeneous matrix contain- 

 ing (1) numerous anastomosing spaces more or less filled with cells, 

 and (2) granular cells which give rise to delicate processes which 

 enter into connection with other granular cells, and with the spaces 

 just mentioned, and with the ectoderm and endoderm. Some sug- 

 gestions regarding the origin and function of these structures will be 

 found in connection with the description of M. tuberculoid which 

 follows. The endoderm of the column is low, and consists of more 

 or less spherical cells, usually containing zooxanthellse. A delicate 

 layer of muscle fibres arranged circularly occurs between the endo- 

 derm and the mesoglcea. 



At the upper part of the column a well-developed double sphincter 

 muscle occurs, imbedded in the mesogloea. It is stronger than that 

 found in Z. sociatus, and more nearly resembles that described by 

 Erdmann 1 and Hertwig 2 in Z. Dance. (?) 



The tentacles, according to the brief notes taken of the living 

 specimens, are " short, 50-60 in number, in 3 rows." My prepara- 

 tions, however, show that the last statement is erroneous, the tenta- 

 cles being arranged in two cycles only. Their ectoderm is not im- 

 bedded in the mesogloea, nor is there a cuticle covering it. The 

 ectodermal muscle processes of the mesogloea are fairly developed, 

 and immediately below them are to be seen, imbedded in the 

 mesogloea, peculiar granular pale yellowish-green cells, the proto- 



1 A. Erdmann. Ueber einige neue Zoantheen. Jen. Zeit. XIX. 1885. 



2 R. Hertwig. Supplement to Report on the Actiniaria. Zoology of the 

 voyage of H. M. S. Challenger. Vol. XXVI. 1888. 



