222 M. C. Mereschkowsky on new Species 



disposed in several layers. The lobed aspect remarked in 

 the interior is to be attributed, I think, to innnersion in 

 alcohol. 



I will now pass to the description of the gonosome or 

 generative bodies. Their number is less than that of the 

 trophosomes (PL V. fig. 1) ; but they are of larger size (length 

 from 2 to 3 millims., breadth about 2 millims.). The gono- 

 phores are oval, truncated at the upper ends, and grow thinner 

 towards their lower extremity, where they lengthen into a 

 short and slender stem, by means of which they are attaclied 

 (PI. V. fig. 2, e). There are never any blastostyles on the 

 hydrorhiza. 



On observing more attentively the gonophores, I have 

 remarked that they consist of a very thin, transparent, and 

 colourless membrane (PI. V. figs. 3, a, 4, c) enveloping a 

 small medusa, which is found there in the different stages of 

 its development. 



It is probable tliat this thin membrane is formed by a con- 

 tinuation of the chitinous envelope of the hydrorhiza. 1 had 

 not the opportunity of studying a full-grown medusa which 

 had already detached itself from the main body ; but its 

 general features may be inferred from an examination of the 

 newly formed gonophores. I here give two figures showing 

 the structure of the medusa. In PL V. fig. 3 we see a rather 

 mature gonophore pressed by a covering-plate, with the slit- 

 sided umbrella and with the velum ; PL VI. figs. 12 and 13, 

 show the transverse section of the same gonophore. 



I have not paid any particular attention to minuteness and 

 refinement in the delineation of these histological details, my 

 principal aim having been to point out the general distribution 

 of the different parts and organs of the medusa, and not their 

 histological structure. 



By these figures we see that the medusa is composed of a 

 bell (PL V. fig. 3, ^), the sides of which are crossed by four 

 radiating canals (PL V. fig. 3, g^, g\ g^, g*), indicated by 

 bands of a darker shade, passing into four tentacles (PL V. 

 fig. 3,y,/^,/'',/"*) ; these four radiating canals unite at their 

 base in one circular canal (PL V. fig. 3, h), from which 

 spring a row of tentacles in the intervals of the four principal 

 tentacles. These latter having been developed at an earlier 

 period, are the largest of the tentacles, of which there are in all 

 sixteen (PL V. fig. 6). 



From the upper part of each of these radiating canals, at 

 the place where they transform themselves into the digestive 

 cavity of the manubrium (which, I confess, I was not able to 

 detect), pi'oceed two sacs, the canals passing between them 



