238 Miscellaneous . 



and true feet, the ciliated fringes of the provisional natatory organs, 

 and the spines, hairs, or filaments which terminate the antennee and 

 the last segment of the abdomen. But in no species, not even in 

 the Lobsters, which, of all Crustacea, are hatched in the most per- 

 fect condition, does this first metamovphosis cause the appearance of 

 the lateral lamince of the caudal fin and the false feet. These 

 organs remain latent, the latter until the second moult, the former 

 until the third. The lateral laminae of the tail, when they first 

 become visible, are in the form of very small oval disks, and the false 

 feet are represented by short, bifid, smooth, rounded appendages ; 

 neither of them acquire the characters which they present in the 

 perfect animal until the fourth moult. 



This is the case with the other organs which are incomplete, rudi- 

 mentary, or deficient at the moment of exclusion ; at each moult 

 some become complete, others acquire more and more their normal 

 form, whilst others make their first appearance, to arrive subse- 

 quently at their final perfection*. 



In conclusion, the author expresses himself as follows : — " The 

 facts which I have just detailed very briefly, facts which I have seen 

 constantly and invariably produced, justify us in thinking that the 

 embryos of Palinurus vulgaris, being subjected to the same meta- 

 morphoses as the larvae of the other marine Crustacea, must, like 

 them, acquire those organs of which they are destitute at birth, after 

 several moults. The investigations which I am engaged in will, I 

 hope, soon enable me to bring evidence in support of this assertion, 

 and at the same time to demonstrate that if the Phyllosomata of 

 authors present more perfect characters than the larva which forms 

 the subject of these observations, it is because these Phyllosomata 

 have already undergone several metamorphoses, and consequently 

 represent subjects in a more advanced state of development." — 

 Comptes Rendus, December 26, 1864, p. 1101. 



On the Eyes o/Asteracanthion rubens, MiilL ^ Trosch. (Uraster 

 rubens, Forbes). By S. Jourdain. 



When we investigate the varied forms of the organ of vision in 

 the Invertebrata, we find that they may be referred to two distinct 

 and fundamental types — (1) the eyes which we propose to call ido- 

 scopic, that is to say, furnishing images, and (2) photoscopic eyes, 

 that is to say, fitted only to give a general sensation of light and 

 darkness. The former, which are met with especially in the Mol- 

 lusca, Insects, and Crustacea, are characterized by an expansion of 

 a nerve of special sensibility, upon which the luminous rays are iso- 

 lated in slender bundles by passing through a very small aperture, 



* The modifications of form produced by successive moults must, in the case of 

 the Phylloaomata, have given origin to many synonyms. The number of the sup- 

 posed species of that form being far greater than that of all the known Palimiri, 

 we are led to suppose that two or perhaps three states of the same larva have 

 been described as so many distinct species. But this is a question which can only 

 be solved by further investigations made in the seas where the Phyllosomata 

 abound, which also can alone teach us to what exotic Palinurus each Phyllosoma 

 belongs. 



