ME. A. V. JENNINGS ON MOBITJSISPONQIA PAEASITICA. 317 



On the True !N^ature of " Mobmsispongia parasitica^ Duncan. 

 By A. Vaughan Jennings, F.L.S., F.G-.S., Demonstrator 

 of Botany and Greology in the Royal College of Science, 

 Dublin. 



[Read 6th June, 1895.] 



In tlie Journal of the Eoyal Microscopical Society for June 

 1880, the late Professor Martin Duncan described an organism, 

 w liich he regarded as " a parasitic sponge of the order Calcarea," 

 and which he named Mobiasispongia parasitica. 



The reasons given for classing the specimen with the Sponges 

 were decidedly inadequate, and writers of monographs on the 

 group have been content to insert the name among doubtful 

 and insufficiently characterized forms. It has become one of 

 those names which reappear in lists compiled by specialists, 

 always followed by a note of interrogation, until some later 

 observation supersedes them. 



As I have been able to examine the original sjjecimen, and 

 believe the appearances necessitate a very dift'erent explanation, 

 I thought it would be of interest to exhibit the preparation to 

 the Society : not only to relieve the students of Sponges of a 

 doubtful genus, but because the form has also a distinct interest 

 for those who are working at the Protozoa. 



Dr. Duncan found the organism in some sections of Carpenteria 

 rJiaphidodendron, Mob., from Mauritius, which had been lent him 

 by the late Dr. W. B. Carpenter. 



It consists of a series of delicate calcareous sacs or chambers 

 connected by straight stolon-tubes, lyiug within one of the 

 chambers of the Carpenteria. Some of the stolon-tubes pass 

 through the partition-wall of the Carpenteria and communicate 

 with sacs lying in the adjacent chamber. The wall both of the 

 sacs and tubes is a thin calcareous shell traversed by well-marked 

 perforations and bearing short pointed spines on the exterior. 

 The group of sacs in the chamber of the Carpenteria measures 

 about a fiftieth of an inch in length by a hundredth in breadth, 

 while some detached sacs may be found in other parts of the 

 slide. 



In 1891 the late Dr. P. H. Carpenter lent me some slides of 

 Carpenteria ioY examination, and in the course of my study of 



LINN. JOUBN. — ZOOLOGY, VOL. XXV. 26 



