VARIOUS POLYZOA. 



449 



the membrane of the upper part of the cell, from which the semicircular edge and lip can 

 recede if pushed from within. 



Suppose, yet again, that in every cradle there lies a baby with its little knees bent up 

 to its chin, in that zigzag posture that children, little and big, often like to be in. But 

 stay, -here is a child moving ! Softly and slowly pushes open the semicircular slit in the 

 coverlet, and we see him gradually protruding his head and shoulders in an erect posi- 

 tion, strengthening his knees at the same time. He is raised half out of bed, when lo ! 

 his head falls open, and becomes a bell of tentacles. The baby is the tenant polype." 



Fig. C is the Toothed Sea Mat, given in order to show the curious toothlike append- 

 ages from which it derives its name. 



POLYZOA. III. 



A. Flustra foliacea. (See Mat.) B. Flustra foliacea. X C. Flustra denticulata. X (Toothed Sea Mat.) 



D. Carbasea episcopalis. X (Bishop's Mitre.) E. Carbasea episcopalis. F. Diachoris crotali. X 



G. Diachoris magellanicus. X H. Membranipora pi!6sa. I. Membranipora pilosa. X 



K. Lepralia Landsborovii. L. Leprulia spinifera. M. Lepralia spinifera. (Ovicell. X) 



N. Lepralia trispinosa. 

 The sign X signifies that the object is magnified. 



At E is seen a curious polyzoon, found in Bass's Straits at a depth of forty-five fathoms, 

 and bearing the name of Carbasea episcopalis. This species is found in two forms, either 

 parasitic on sertularia and various polyzoa, and then of small size, or leading an inde- 

 pendent existence, and reaching considerable dimensions. It is chiefly remarkable for 

 the singular form of the ovicells, which bear a wonderfully close resemblance to bishops' 

 mitres, and have earned for the species the title of episcopalis. A group of these ovicells 

 may be seen at fig. D. 



Two specimens of another genus maybe seen at figs. Fand G, the former representing 

 a single cell of Diachoris crotali, for the purpose of showing the remarkable appendages 

 which guard the mouth ; and the later, Diachoris Magellanicus, exhibiting the method in 

 which each cell, except at the margins of the fronds, is connected with six others, 

 something like the stellate cells in pith. In fact, the Diachoris is a flustrum dissected, 

 the cells being drawn away from each other and connected by stalks. In the illustra- 

 tion, the connecting stalks are well shown, by which the central cell is united to the six 

 that surround it, and several of the avicularia are also given. 



Any one who picks up a piece of a dark seaweed, will find that many parts of -its 

 structure are covered with a peculiar growth, that looks as if a portion of Sea Mat had 

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