278 NOTES AND MEMORANDA. 



marine protozoic fauna differs far more in different seas than does 

 the fresh- water protozoic fauna in different terrestrial regions. 



Deep-sea Siphonophora. — The Siphonophora have always been 

 held to be an exclusively surface group ; it is therefore of great 

 interest to find species of the sub-order occurring at great depths. 

 Professor Studer of Bern gives an account * of two well-marked species 

 brought up di;ring the voyage of the corvette ' Gazelle,' from depths of 

 1500-2000 fathoms in the Atlantic Ocean. Both species belong to 

 the genus Bhizophysa, and are named by Studer B. conifera and B. 

 inermis. Full descriptions, illustrated by three plates, are given of 

 both forms, as well as of some fragmentary sj)ecimens of other 

 Siphonophora found at the same time. 



Strange Anomaly among the Hydromednsae.— In the ' Transac- 

 tions of the Society of Naturalists of St. Petersburg,'! a new species of 

 small naked-eyed Medusa, from the White Sea, is described, which 

 Mereschkowsky has named Bougaiuvillea paradoxa, and which (with 

 another species of the same genus) presents a strange anomaly pretty 

 frequently observed amongst the normal individuals. 



The adult animal does not much exceed 1 cm. in length, and 

 its form is that of a bell slightly contracted at its aperture, with four 

 radiating canals, each furnished at its extremity with a tuft of from 

 three to seven tentacles and with a red ocellus. The deep red manu- 

 brium has from above the form of a cross, from each of the four ends 

 of which starts a radiating canal. Round the mouth there is a circle 

 of four tentacles dividing dichotomously into a great number of 

 branches. It is remarkable that the ova are developed immediately 

 on the surface of the manubrium, so that the latter when the ova have 

 become converted into planulie acquires a tuberculate aspect, caused by 

 a great quantity of planulee forming a layer covering its surface, with 

 one of their ends projecting freely, and the other attached to the wall 

 of the manubrium. 



Some forms (undoubtedly of this same animal) are distinguished by 

 the total absence of the coloured manubrium. It was thought that 

 there might be some atrophy of the organ, but remains of it were 

 sought for in vain. The whole gastro-vascular system consisted only 

 of a circular canal and of the four radial canals, which were united at 

 the summit without forming anything resembling a stomach. More- 

 over, although in other respects of normal conformation, it had abso- 

 lutely no opening to the exterior, no buccal or other aperture which 

 might establish a communication with the circumambient water. 



This fact is the stranger because these anomalies are observed in 

 MedusiB which are but very little exceeded in size by the normal 

 adult individuals. They consequently liave been able to nourish 

 themselves, since from microscnpic embryos they have attained a size 

 of more than half a centimetre. 



M. Mereschkowsky considers that the only probable hypothesis 

 to account for the development of a complete Medusa, without the aid 



* ' Zeitschrift f. wiss. Zool.,' xxxi. (1878) 1. 



t ' Protocolles de la Reunion du 14 Jau. 1878,' ix. 33. 



