ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 793 



reminds us that Peltogaster is curved en itself, that it is fixed to its 

 host hy a small pedicle, which varies a little in position and has at 

 the other end the cloacal orifice. 



It is of a rosy colour, but becomes a reddish-orange when, as is 

 often the case, it is full of ova. It is from 2 or 3 to 12 or 15 mm. in 

 size. It has a very marked general resemblance to a Sacculina, but 

 differs in some important points. The mesentery is not flattened, 

 but very wide ; the two membranous folds of which it is formed are 

 not closely appressed, but separated by a mesenteric canal. The 

 testes are a little nearer the pedicle, and their crecal termination is 

 not swollen but gradually tapers and loses itself in the adjoining 

 connective tissue ; their deferential orifice is much larger than that 

 of Sacculina. The cement-glands are not, as Kossmann thought, 

 absent, but are really very large. The ganglion which forms the 

 sole representative of the central nervous system, is situated in the 

 mesentery, in the sagittal plane between the pedicle and the cloaca, 

 but is much nearer the former. The ganglion is so small and the 

 surrounding connective tissue is so like it that it is almost impossible 

 to make it out in a fresh specimen. 



Specimens should be macerated in a 12 per cent, solution of nitric 

 acid for three or four days, when they are relatively easy to dissect ; 

 the connective tissue is thus rendered very fragile, and is partially 

 destroyed, the albuminoid substance of the ova is coagulated, and 

 the ova formed into a solid mass which can be easily removed ; the 

 ganglion and nerves become tinged and much easier to see. 



The ganglion is a small fusiform elongated mass, about 1 mm. in 

 size and branched at its end ; it is imbedded in connective tissue. It 

 gives off three groups of nerves : an anterior, which contains four pairs ; 

 a lateral, in which there is only one pair ; and a posterior, formed by 

 a single unpaired nerve and its ramifications. In the median line the 

 first group gives off a pair of very fine and long nerves, which extend 

 along the mesentery, in the midst of the connective tissue, as far as 

 the cloaca ; they penetrate into the muscular substance into which 

 they can be traced for a certain distance ; they evidently terminate 

 in the muscles of the cloaca, and especially in the sphincter ; and they 

 may be called the cloacal nerves. At the sides there are the paired 

 anterior and lateral pallial nerves ; the ovarian are given off from the 

 anterior extremity of the ganglion, and are exceedingly delicate. 

 The lateral group forms the parieto-visceral of either side, and its 

 chief branch is the nerve of the cement-gland. The posterior group 

 contains a large trunk which may be called the pallio-visccral nerve ; 

 this, near its origin, gives off a pair of very fine branches which 

 supply the testes and their deferent canal. The author gives a brief 

 notice of the histology of the nerve-fibres and cells. 



The mantle of Peltogaster is formed, as in Sacculina, of nucleated 

 epithelio-connective fibres, among which is a plexus of muscular 

 fibres ; the ovary, as in the allied form, consists of two lobes, and the 

 testes of two tubes. The cement-glands are very large, and differ in 

 position and constitution from those of Sacculina : the difference in 

 position is due to the ovary opening at the level of the incubatory 



