92 ENTOZOA. 



been very carefully anatomised by Mr. Busk, from whose drawings 

 the accompanying plates have been executed. Probably several 

 other species will be discovered wlien the lungs and cranial 

 sinuses of the larger cetacea are carefully examined for this 

 purpose. The form (P. convohUus) here represented is the least 

 known of the three infestmg the porpoise. On the Continent it 

 has only been dissected by Kuhn and Bschricht, whilst the other 

 species have not only been examined by these authors, but also by 

 Raspail, Dujardin, Von Siebold, Van Beneden, and several others. 



According to previously published observations, the male of 

 P. convol'iitus acquires the length of an inch, but in Mr. Busk's 

 specimens one was fully fifteen lines long, whilst from the condition 

 of the internal reproductive organs he was even led to believe that 

 it was not quite fully grown. To the naked eye, and also under 

 magnifying glasses of considerable power, the surface of the body 

 appears smooth, but under the one-inch objective, fine transverse 

 stride are visible at all parts of the body. In the immediate neigh- 

 bourhood of the mouth, when the worm is viewed from above, these 

 strise form a regular series of concentric circles, surrounding the 

 mouth, which occurs in the condition of a simple rounded aperture 

 devoid of any prominences or lips. In the male (Fig. 1, Plate VI.) 

 the head is abruptly truncate, uniform and continuous with the 

 trunk ; but in the female (Fig. 1, Plate VII.) it is decidedly pointed, 

 the conical neck or upper end of the body being bordered by a 

 somewhat irregular folding or twisting of the thick diaphanous 

 epidermis. This appearance is not only peculiar, but is believed to 

 be distinctive of the species. At other regions of the body in the 

 female this prominence of the transparent cuticle is less marked, 

 but at the caudal extremity, both above and below the anal orifice, 

 similar diaphanous foldings occur (Figs. 2 and 3, Plate VII.) In 

 the male P. convolutus the outer integumentary layer is uniformly 

 developed and closely applied to the dermis over the whole anterior 

 and middle part of the body ; but on approaching the tail, the 

 epidermis suddenly spreads out on either side to form a pair of 



