60 



Tlu' eiulood'ciiiiii, as in llu' loii'i^oiiij; i^roup, is I'oniu'd l)y llif dislai wail iii'- 

 tween two chambers lying in llu- same longiliulinal row, bul while the ecto- 

 oa>ciiiin in that groii]) was only represenled by a more or less distinctly limited 

 part of the frontal mcmiirane of the covering zoo'cinm, it is here so lo speaii 

 represented by the whole covering chami)c'r, which is a Ucno/Od'ciuni. W'c find 

 everywhere a common operculum for the kenozorecium and the owcium. Such 

 oa'cia are found in Didymia simplex (PI. IV, fig. 7 d), Eiwratea chelata, likcllarin 

 infnndilnildld (PI. IV, figs. 4 a— 4 d), Menipea crijstallinu (PI. IV, ligs. 1 a, 1 b), 

 Ciiltiilinit piincldld (PI. IX, iig. lib), Cr. dnnnlatd, Cr. (idltijiiv (PI. I\, lig. 12a), 

 Escharella diiiphana (PI. XVII, fig. 1 a), Ksch. abyssicoUi (PL XVII, lig. 2 a), 

 Enriistonielld fordimnicierd (PI. XVIII, figs. 14 a — 14 b), E. hilahidtd, besides in the 

 Farciminarid species (PI. I, figs. 10 a — 10 c), most members of the family Catena- 

 riidae (Pis. XI, XII, XIII, XV), and the members of the family Ilippothoidae 

 (Pi. XXI, figs. 8e, 8 b, 9 a, 9 c). 



The fact that the endoooecial ocecia, besides appearing as a rule in certain 

 families, appear sporadically in more or fewer forms in a number of other 

 families would seem to suggest Ihal they rei)resenl an old oau'ial type, which 

 perhaps was at some lime general, but which later has been replaced 1)\' others. 

 It deserves to be mentioned in this connection Ihal they apjjcar together with 

 hyperstomial (xrcia in Cribriliiia punctdtd (1^1. IX). 



2) The hyperstomial ooecia (PI. XXIV, figs. 12 — 18). These oa>cia like the 

 endozocecial consist of an endoooecium and an ectoooecium, which join at the 

 free frontal edge of the o<rcium and form together a fold, the oa'cial Ibid: but 

 they are always situated outside the cavity of the zooecium, and the dislai wall 

 does not take part in their formation, even though they most frequently arise 

 from or in the immediate neighbourhood of its fiontal edge. The two layers 

 of the actual oieciuui are formed by the frontal membrane of Ihe distal zoo'cium, 

 hut between these a cryplocyst layer may sometimes appear, and in many cases 

 the hyperstomial on-cia are pro\ided with an oo^cial cover. This type of onH-ium, 

 which aj)pears in the majority of Ihe Cbeilostoiudld, presents numerous modifica- 

 tions, of which we may mention here Ihe mosl important, bul for the rest refer- 

 ence may be made lo the dilTereiil I'amilles. 



We may begin with the oo'cia in Scriipocellarta scabra, of which a series 

 of developmental stages have been figured on PI. II, figs, f) a— 5 f, as they 

 appear when the colony is viewed from the surface and after treatnieni with 

 boiling alkali or cold eau de Javelle. At the time when the frontal wall of the 

 distal zooecium is still ciuite membranous, the first trace of the calcium appears as 

 two small dislai rounded calcareous plates, which arise from the frontal edge of 



