496 Dr. H. A. Mcliolson and Mr. A. H. Foorcl on 



EXPLANATION OF PLATE XIV. 



Fig. 1. Transverse section (male Gastrosteus sp.) of renal mass, urinary 

 bladder &c. in situ, X 150 diam. A, kidneys (coalesced por- 

 tion) : a, a, right and left ureters passing longitudinally along 

 outer ventral borders of kidneys ; b, urinary tubules, nuclei of 

 epithelial cells indicated. B, urinary bladder, behind the cervix : 

 a, epithelium ; b, fibrous layer ; c, c, right and left ui-eters (on 

 opposite sides of bladder) ; d, contained thread-like secretion 

 from kidneys ; C, intestine ; D, D', testes. 



Fi(/. 2. Fragment of hyaline capsule of ovum, shovping the rovs^s of pits 

 and lamellae, X 300. 



Fig. 3. Ditto, in transverse section, shovring numerous lamellse, X 350. 



Fig. 4. Portion of mucous secretion, showing funicular structure, X 350, 



Fig. 5. Sketch of nest (diagrammatic), one third nat. size, the pockets 

 containing ova exposed. a, a, transversely-arranged inter- 

 secting threads ; 6, b, masses of ova contained in the interspaces 

 of nest. 



Fig. 6. Dissection of male, showing viscera of posterior portion of abdo- 

 minal cavity, about nat. size, a, enlarged urinary bladder j b, 

 left flexure of ditto (cervix) ; c, right flexure of ditto (near 

 posterior termination) ; d, genital pore ; e, cloacal depression ; 

 J, anus : g, urinary apertm'e ; h, alimentary canal ; ^, i, right 

 and left testes ; j, j, kidneys ; j 1, ureters ; k, swim- bladder. 



XLIX. — On the Genus Fistulipora, M^Goy^ with Descrip- 

 tions of several Species. Bj H. Alleyne Nicholson, M.D., 

 - D.Sc, Regius Professor of Natural History in the Univer- 

 sity of Aberdeen, and Aethue H. Fooed, F.G.S., late of 

 the Geological Survey of Canada. 



[Plates XV.-XVIIL] 



Inteoduction. 



In the course of our study of various species of Fistulipora 

 a most interesting and suggestive structural feature has come 

 under our observation. This consists of a very peculiar 

 modification of the walls of the autopores *, which gives them 

 quite a distinct /ac^es, and as it appears to have an important 

 bearing upon the question of the zoological affinities of the 

 genus (and consequently upon that of the Monticuliporidas in 

 general) we shall describe it as minutely as possible. 



* We avail ourselves of this opportunity to ofier a few words of expla- 

 nation to the reader with reference to this and other terms we have found 

 it expedient to introduce in substitution for the older ones hitherto iu 

 use. The principal tubes in Fistulipora and other genera of the Monti- 

 culiporidas have been called " large coralhtes," or simply " corallites ;" 

 the tubes or tubuli filling the interspaces among these received the name 

 of " interstitial tubes ;" while the minute tubuli situated at the angles of 



