132 



PROF. G. J. ALLMAK OlST LIMNOCODITJM YICTOEIA. 



The marginal bodies are about 128 in number, and consist of a 

 highly refringent spherical corpuscle surrounded by a delicate trans- 

 parent capsule. This capsule is very remarkable, for, instead of pre- 

 senting the usual spherical form, it is of an elongated piriform shape. 

 Inits larger endislodgedthe spherical refringent body,anditthence 

 becomes attenuated, forming a long, tubular, tail-like extension, 

 which is continued into the velum, in which it runs transversely 

 towards the free margin of this membrane, and there, after becom- 

 ing more or less convoluted, terminates in a blind extremity (fig. 3). 



The reproductive sacs are borne on the radiating canals at a 

 short distance beyond the exit of these from the manubrium. 

 They are of a piriform shape, and spring by their narrow ends from 

 the canal, whence they hang down free into the cavity of the um- 

 brella. Their colour is a brownish yellow, derived from the 

 pigment-cells developed in their endoderm. 



The manubrium is of a similar brownish -yellow colour, due also 

 to the pigment-cells of its endoderm. 



Fig. 1. 



The following notes have been made 

 since the above was received : — 



The attachment of the tentacles is 

 peculiar. Instead of being free con- 

 tinuations of the umbrella-margin, they 

 are given off from the outer surface 

 of the umbrella, at points a little above 

 the margin and at three or four different 

 levels. From these points, however, each 

 maybe traced centrifugally in the form of 

 a ridge as far as the thickened umbrella- 

 margin (fig. 1). This ridge consists of the 

 proximal portion of the tentacle, which is 

 here adnate to the outer surface of the 

 umbrella. It holds exactly the position of 

 the " Mantelspangen," or jperoni 

 developed in the whole of the Narcome 



Diagrammatic meridional 

 11 section of Medusa through a 

 " /U radial canal. 



u, umbrella; on, thickened 

 dusge of Haekel and in some genera of his and pigmented margin ; v, 

 m , i * tj- j- x i velum ; I, hthocyst ; r, radial 



Trachomedusae*. Its structure, however, canal; c, circular canal; n, 

 differs from that of the true perooiia, which nerve-ring; t, tentacles; 

 are rib-like lines of thread-cells marking ' 



* Eelations of ' Idonoiocodiuon to the Trachomedusse are maintained by Prof. Lan- 

 kester, who refers the medusa to the Trachomedusal family Petasidce. See 'Nature ' 

 for June 17, 1880, and his paper of the same date read at the Eoyal Society. 



