ZOOLOGY AND BOTANT, MICROSCOPY, ETC. 939 



is by no means adapted to carrying waves of sound ; they are very generally 

 connected with cellular outgrowths which are necessarily pressed upon 

 when the equilibrium of the body is disturbed. These considerations may 

 be extended to the Yertebrata, and it is suggested that the crista acousticae 

 of the ear with which no otoliths are connected may perform the acoustic 

 functions of the ear, while the macuLne acousticas have an equilibrating 

 function. The well-known observation of Hensen as to the casting of the 

 otoliths in certain Crustacea seems to be of great significance in connection 

 with the real function of these organs. 



B. INVERTEBRATA. 



Pericardial Gland of Opisthobranclis and Annelids.* — Prof. C. Grobben 

 endeavours to demonstrate the homology of the pericardial gland of Molluscs 

 with structures which are found in Annelids. He points out that the peri- 

 cardial gland of Molluscs is a local glandular development of the epithelium 

 of the secondary ccelom, as the pericardial space must be regarded as being. 



Similar glandular difierentiations of the ccelomic epithelium are to be 

 seen in the chlorogogue cells of many Annelids, and they too are found on 

 the blood-vessels. In some cases these bodies form special organs ; they 

 are best developed in the well-known tubular contractile appendages of 

 the dorsal vessel of the Lumbriculidfe, and the structures described by 

 Claparede in Lumhricus as best developed on the vascular loops of the septa 

 are bodies of the same kind. The excretory fimction of the pericardial 

 gland and epithelium is best shown in the ^Tilollusca : these are cells heavily 

 laden with concretions which can hardly make their way to the exterior save 

 by the kidney ; similar bodies escape outwards by the nephridia in Annelids. 



Singular Parasite on Firola.t— Prof. H. Ludwig has a note on the 

 remarkable parasite in Firola (Trichoelina paradoxa), lately described by 

 Dr. J. Barrois4 showing that it is nothing more than the separate capitulum of 

 a gemmasform pedicellaria, and almost certainly of Sphserechinus granularis.^ 



Mollusca. 



Structure of Branchia of Prosobranchiate Gastropoda. |1 — M. F. Ber- 

 nard has investigated the structure of the gill of various prosobranchiate 

 gastropods. He finds that the epithelium always consists of two kinds of 

 elements — columnar ciliated cells, inserted on a basilar membrane bv a 

 narrow prolongation which is sometimes branched, and muciparous cells 

 arranged in small scattered groups. The basilar membrane does not 

 contain any cartilage ; what has been regarded as such is a thickenincr 

 formed of superposed layers, and contains no trace of cells. Between the 

 two layers of the membrane are stellate cells, with anastomosing pro- 

 longations ; these, which may be isolated or connected, form the ordinary 

 connective tissue of the lacunae. There are longitudinal and transverse 

 muscular fibres. 



Although the author has been able to reproduce the appearances fifriired 

 recently by M. Wegmann, he does not believe that the '• vessels " are anythincr 

 more than portions of the lacunas where the connective tissue is scattered, 

 and where therefore the injection circulates easily. The space contained 

 by the double basilar membrane is only a simple diverticulum of the 

 general lacuna which extends between the two folds of the mantle. 



* Zool. Anzeig., x. (18S7) pp. 479-81. t Ibid., pp. 296-8. 



X See this Journal, ante, p. 373. 



§ This note, owing to a misprint, was wrongly placed at p. 598, and Trichodina was 

 printed for Trichoelina. \\ Comptes Kendus, cv. (1887) pp. 316-8. 



