340 



ZOOLOGY. 



which plauts of t'he Victoria rcgia were growing in the garden of that 

 society. The water in the tank had a temperature of about 90<^ F., and 

 was literally swarming with the little medusae, the larger of which 

 measured nearly half an inch in transverse diameter. They were very 

 energetic in their swimming, and displayed the characteristic systole 

 and diastole of the umbrella, and were nourishing apparently in the very 

 conditions which contribute most completely' to their well being. Speci- 

 mens of this form were obtained by Profs. E. Ray Lankester and Geo. 

 G. Allmann, and described by the former June 17, and by the latter June 

 24, in "Nature"; by the former, under the name Craspedacusta Soicerhii. 

 and by the latter as Limnocodium Victoria. Subsequently an attempt 

 to compromise on the name was made, and Professor Lankester desired 

 to perpetuate the designation of Limnocodium Sowerhii. Inasmuch, 

 however, as Craspedacusta was first used and accompanied by a satis- 

 factory diagnosis, there can be no question but that conformity with 

 the laws of nomenclature compels its retention. The most characteristic 

 feature of the new form is the development of otoliths and velar canals. 

 The otoliths are " placed along the line of insertion of the velum — about 

 80 in number (fewer in small specimens). From 10 to 20 are placed 

 between successive perradial tentacles arranged in groups of two or three 

 between the successive secondary tentacles." The velar centrifugal 

 canals " (which are really the elongated otocysts) are peculiar to this 

 genus ; passing from the otoliths (one inclosing each otolith) into the 

 velum, and then ending blindly. They appear to correspond to the 

 centripetal canals found in other Trachomedusae, in the disk." By Pro- 

 fessor Lankester it is claimed that Craspedacusta belongs to the family 

 Petasidae among the Tiachomedusae, which are distinguished by the 

 development of '■'■four radial canals, in the course of which four gonads 

 lie, with a long tubular stomach, and no stomach-stalk." According to 

 Professor Allmann, however, while some of the characters "point to an 

 affinity with both Trachomedusa; and Narcomedusae, this affinity ceases 

 to show itself in the very important morphological element aflbrded by 

 the marginal bodies. In both Trachomedusae and Narcomedusae the 

 marginal bodies belong to the tentacular system ; they are metamor- 

 phosed tentacles, and their otolite cells are endodermal, while in the 

 Leptomedusae, the only other order of craspedototal Medusae in which 

 marginal vesicles occur, these bodies are genetically derived from the 

 velum. Now, in Limnocodium the marginal vesicles seem to be as truly 

 velar as in the Leptomedusae. They occur on the lower or abumbral side 

 of the velum, close to its insertion into the umbrella, and the tubular exten- 

 sion of their capsule runs along this side to the free margin of the velum, 

 while the delicate epithelium of the abumbral side passes over them, as 

 in the Leptomedusae. It is true that this point cannot be regarded as 

 settled until an opportunity of tracing the development is afforded ; but 

 in very young specimens which I examined I found nothing opposed to 

 the view that the marginal vesicles were derived, like those of the 



