of Mollusks in Holothurise. 23 



such, for example, as the muscular stomach, the muscular bundles 

 in the mesentery (with whose movements Quatrefages was ac- 

 quainted), and the existence of many peculiar ciliary organs, 

 j^th of a line in length, attached to the mesentery, the general 

 surface of which is not ciliated. 



The pedicles of these organs have the same structure as the 

 peritoneum, consisting of a simple glassy membrane in which 

 nuclei are scattered, and which is continued over the outer sur- 

 face of the organs. The structure of these organs is complicated, 

 and could be more readily explained by figures than by any de- 

 scription ; to call them slipper-shaped, or like a cornucopia, would 

 perhaps give the best geueral idea of their outward form and 

 of their cavities clothed with long active cilia. 



When at the commencement of the present year I had an op- 

 portunity of procuring this Synapta digitata in great numbers at 

 Trieste, I found ova in all the individuals, whence the statement 

 of Quatrefages, that these animals are hermaphrodite, seemed 

 confirmed ; a circumstance which surprised me no little, inasmuch 

 as the other families of Echinoderms are without exception di- 

 oecious. 



In summer, when I renewed my investigations at the same 

 place, I found the several oi'gans of almost all in nearly the same 

 condition as in spring, but less turgid. 



The ova were about fa to J^ of a line in diameter ; in spring 

 they measured as much as yytn of a line. The yelk is very finely 

 granulous, and contains a germinal vesicle — which has no ger- 

 minal spot such as Quatrefages depicts. The dichotomously 

 branched ovarium is rendered yellow by the ova ; its innermost 

 layer was formed as in spring by cells ^^th *° 2Fo* n °f a nne 

 in diameter, from which, according to Quatrefages, the sperma- 

 tozoa are developed. 



About the middle of August I met for the first time with an 

 individual with a totally different generative organ. This was 

 much thicker and unbranched, of a green colour for one moiety 

 of its length, while the other was orange ; the latter portion con- 

 tained ova with a germinal vesicle, and without any germinal 

 spot, but they were larger (yj^ n line), and very different in ap- 

 pearance ; their yelk was coarsely granular, the granules being 

 partly round and partly oval, dark-coloured, and having the ap- 

 pearance of the so-called stearine-granules of the frog's ovum : 

 they were T i n to 2nu tn °f a nne m diameter. 



When I observed this, I began again to doubt the herma- 

 pbxodism of the Synaptce, and I conceived that either these, or 

 the other more numerous individuals, must be the males ; I there- 

 fore caused great numbers of Synapta to be brought to me daily, 

 and soon found individuals similar to those last described ; but to 



