202 Miscellaneous. 



times as thick, iu certain cases even equal iu thickness to the stem. 

 They present the two layers which constitute the walls of the body, 

 and contain a prolongation of its cavity. They are present only on 

 a small number of hydranths, about one ninth of the whole. They 

 are capable of movement, as, indeed, is indicated by the presence of 

 a strongly-developed muscular layer, and are furnished with a great 

 abundance of urticating organs, whence the name of cmdojjihores 

 given to them by Dr. Weismanu. These urticant cap.siiles are more 

 especiallj' grouped at the extremity of the cnidophore, where they 

 form several layers among the cells of the ectoderm. In the deei^er 

 layers of the endoderm there are subepithelial cells giving origin to 

 circular muscular fibres which present nuclei, and upon which a 

 striation is observed hero and there. 



The cnidophores only make their appearance in hydranths which 

 have attained their full development. They show themselves first 

 of all in the form of an elevation of the ectodermic wall, situated upon 

 a small annular projection which occui's at the lower part of the calyx, 

 and which Dr. \V eismann calls the urticant wall (^Nesselwall). This 

 name has been given to it because it is the j)art of the calyx which 

 contains the greatest quantity of urticating organs, at any rate in 

 Eudendrium ramosum. Below this urticant wall there is an annular 

 groove ; and immediately beneath this groove is seen what Dr. 

 Weismann calls the (jJandidar ring (Driisenring). At this point 

 the ectoderm only presents a layer formed of cells which produce a 

 viscous secretion. 



If, on the one hand, it is evident that the cnidophores are power- 

 ful weapons for the hydroids M^hich possess them, on the other it is 

 difficult even for so sagaciotis a naturalist as Dr. Weismann to 

 understand their special use, since they are the appanage of only a 

 small proportion of the hydranths of a colony. 



There are two points to be noted with regard to these singular 

 organs — namely, that they do not occur in the other species of Eu- 

 dendrium, and that they occupy a completely asymmetrical position. 

 The author compares the cnidophores with certain structures met 

 with in the Hydractinidte, the Plumularidte, the Millepoiida3, &c., 

 and which one might be tempted to regard as their homologues. 

 He shows that they differ from these completely from a morpholo- 

 gical and histological point of view, and that we have to do here 

 with organs of a special nature. — Mittheil. aus der zool. Stat, zu 

 iieapel, vol. iii., 18bl ; Bibl. Univ., Arcli. des Sci., January 15, 

 18«2, p. 103. 



Note on the Pearly Organs of Scopelus. 

 By H. B. Guppx, M.B., Surgeon li.N, 



Dr. Giinther* has called upon travellers to examine fresh speci- 

 mens of pelagic fishes provided with " luminous organs," in order to 

 ascertain, if possible, the functions of these organs, and also to dis- 

 cover whether or not the luminosity (if such be their function) is 



* ' Introduction to the Study of fishes/ p. 70G. 



