Dr. H. Burmeister on his so-called Globiocephalus Grayi. 51 



how he found thread-cells in Reniera Jibulata and Desviacella 

 vagabundaj seemg that many thousands of microscopical ex- 

 aminations of the Spongiadai have been made by different 

 naturalists up to this time without their observation. 



The Renierin^e are especially subject to surface polype 

 parasites, and none more so, perhaps, than J?e?i«e?"a^^'ii(/ate, Sdt., 

 all over the world. (This species is characterized by two forms 

 of spicules, viz. (1) acerate, curved, smooth, large, and (2) C-& 

 S-shaped, minute.) But I have never before found a parasitic 

 polype in the interior of a Reniera or any other sponge, and 

 never any thread-cells where there were no parasitic polypes 

 to originate them. Nor should I have been able to detect 

 them now but for the process mentioned. 



There is also another jar sent me by Prof. W. Thomson, in 

 which there is a portion of the same sponge with three other 

 small fragments of as many species undescribed ; but this is 

 labelled " Adventure Bank, 92 faths." 



" Bon Bay " is on the African coast, opposite Cape Sparti- 

 vento (Sardinia) ; and "Adventure Bank" is the shoal between 

 Tunis and Sicily. 



Prof. Thomson also adds the following interesting informa- 

 tion respecting thi'cad-cells, in a note just received : — 



" Thread-cells are abundant in every thing which feeds upon 

 Coelenterates of any kind, young or mature, whether feeding 

 by cilia or by the mouth. I have found the thread-cells of 

 several Hydroids apparently living in the skin of a Synajyta ; 

 and you can always find plenty of them in Amphidetus. Of 

 course, if you find a parasitic polype in the sponge, there is no 

 further difficulty ; but that does not seem necessary. Thread- 

 cells appear to be able to live, for a time at least, an indepen- 

 dent life in foreign quarters." 

 June 17, 1872. 



V. — On my so-called Globiocephalus Grayi. 

 By Dr. Hermann Burmeister. 



In the new ' Journal de Zoologie,' the editor. Prof. Paul Ger- 

 vais, of Paris, has noticed (tome i. p. 68) the descriptions of 

 Cetacea published by myself in the ' Anales del Museo Publico 

 de Buenos Aires,' tome i. p. 367 et seqq.^ and has hinted, with 

 good reason, that the animal described there as GloMocephalus 

 Grayi is not a Glohiocephalus^ but a Pseudorca^ nearly allied 

 to, if not identical with, Ps. crassidens of Prof. Eeinhardt 

 (Overs. Kongl. Danske Vidensk. Selsk. Forhandl. 1862, p. 103 

 e^seg'^'.)^ comparing my figures given on pi. 21 of the 'Anales' 



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