Miscellaneous, 331 



of the mandiblefl ; m.v. 1, part of first maxilla ; 7/1.17;., maxilli- 

 peds ; gn. 1, first gnatliopod, omitting the large basal joint; 

 gn. 1, B, first gnathopod from another specimen, finger and part 

 of hand ; (jn. 2, second gnathopod ; prp. 5, fifth perseopod ; 

 pip. 4, fourth pleopod ; ur., uropod ; t, telson. 



MISCELLAJ^EOUS. 



JS'ote on Parmacellus gracilis, Gratj. 



In 1855 (Cat. Piilm. Brit. Mus. part 1, p. 64) there appeared the 

 description of a slug under the name of Parmacellus yracilis. This 

 species, which was based on a specimen purchased with the label 

 '■'■Parmacella Olivieri" in the collection of the British Museum, has 

 never since been recognized. The locality was unknown. 



Last year, while examining the slugs in the British Museum, I 

 found a specimen oi Ibi/cus fi'ssidens (=siJcl-iineasis) with the label 

 '■'■ParmaceUa. 43. 3. 31. 33," which was entered in the accession- 

 book as '•'■Parmacella OUvieri^ purchased at Stevens'." I described 

 this slug in Ann. & Mag. Nat. Hist., Jan. 1891, p. 106, as /. silckhn- 

 ensis ,=-fissidens ; but it never occurred to me at the time that it 

 was the original of Parmacellus gracilis. Having now compared 

 my notes with the original description, it is evident that these are 

 the same thing. The history of the specimen, with its label, together 

 Avith the general agreement of the described characters, is con- 

 vincing. 



The synonymy will accordingly stand : — 



Ihycus gracilis (Gray, 1855). 



= I.Jissidens (Heyn., 1862). 

 = I. sikkimensis (G.-Aust.). 



Institute of Jamaica, Kingsttin, Jamaica, 

 August 18, 1801. 



T. D. A. CoCKERELT.. 



On the Development of Sponges (Spongilla fluviatilis). 

 By M. Yves Delage, 



I, Formation of the Ectoderm. — M. Goette, of Strasbourg, in his 

 work on the development of the Freshwater Sponge, states that 

 the larval ectoderm is thrown off, and that the permanent external 

 membrane is formed by the superficial layer of the internal meso- 

 dermic mass. All previous authors, on the contrary, affirm with 

 Ganin that the larval ectoderm is transformed into the permanent 

 one, and recently this view has been re-established by M. Maas, of 

 Berlin, who describes in detail the phenomena of the transformation. 



I showed last year * that in Esperella, a genus of siliceous 

 marine sponges, there exist among the ciliated cells of the larval 

 ectoderm large non-ciliated cells, which pass to the surface 

 after the larva becomes fixed, and form the permanent ecto- 



* ' Comptes Rendus,' stance of March 24, 1890. 



