DRS. CARPENTER AND CLAPAREDE ON TOMOPTERIS ONISCIFORMIS. 67 



disguise its form. Nor is this any exaggeration of the fact : for having sent the vessel to 

 an accomplished artist already named, Mr. Peter Syme, for the purpose of obtaining a 

 delineation, I found, on reaching him, that he had been unable to discover the object. 

 However, by resorting to similar expedients as practised by myself, he could now repre- 

 sent the most conspicuous parts of the animal. 



" Nearly three years afterwards, I obtained another specimen in November. Both 

 occurred in a capacious jar of sea-water taken from about the same place, Newhaven 

 Pier. But, with ample opportunities, none have been again found there. 



" Twenty years later, six specimens were obtained from the Isle of May, not less than 

 thirty miles distant ; and from the whole I have been able to gain some slight acquaint- 

 ance with this singular animal — singular because human vision can scarcely discover, 

 what is of sufficient size to expose every feature. Hence it is that there must always be 

 slight discrepancies between the dramngs of different artists." 



Of the two representations given of the animal in Sir J. G. Dalyell's 36th Plate, that 

 which was drawn by Mr. Syme from the specimen first seen departs greatly from its true 

 proportion, — the pinnulated appendages, of which there are sixteen on either side, being 

 drawn much too long (as in the figure of MM. Quoy and Gaimard), whilst the second 

 antennae are as much too short. The caudal prolongation in this specimen appears to have 

 been just beginning to show itself. The second figure, which appears to have been 

 drawn from the specimens obtained at a later period, is a much truer representation of a 

 more advanced stage of development, the length of the caudal prolongation being about 

 one-third of that of the body. Some of the specimens are said by Sir J. G. Dalyell to 

 have had only four or five, or seven, pairs of limbs. He remarks that the animal " can be 

 preserved with difiiculty, from being liable to entangle itseK in every foreign substance, 

 and is easily mutilated in its struggles for liberation. None have survived longer than 

 twenty-four days ; they generally live only a week." We have have not ourselves succeeded 

 in preserving them for more than the shorter of the periods just named. 



EXPLANATION OF THE PLATE. 

 Tab. VII. 



Tomopteris onisciformis. 

 Fig. 1. Posterior portion of the body, and caudal prolongation, of a female, showing the ova in various 



stages of development, lying in the perivisceral cavity. Magnified 40 diameters. 

 Fig. 2, Caudal prolongation of a male, shovcing the testes a, a occupying the cavities of the rudimentary 



pinnulse. Magnified 65 diameters. 

 Fig. 3. One of the testes, more enlarged, showing at a the orifice through which the spermatozoa are 



discharged externally, at b the orifice leading to the perivisceral cavity, and at c the larger 



ridged rosette of the ciliated canal. Magnified 150 diameters. 

 Fig. 4. Biflagellated spermatozoa. Magnified 300 diameters. 

 Fig. 5. Portion of the head, seen on its dorsal aspect, showing the ciliated epaulettes a, a. Magnified 65 



diameters. 



K 2 



