446 Mr. S. 0. Eidley on Fr ecus- Joseph- Land 



Memhranipora SopJiice, Busk. 

 (PI. XXI. fig. 2.) 



Memhranipora Sophice, Busk ?, Quart. Journ. Micr. Sci. iii, p. 255, pi, i. 

 fig. 7. 



I have little doubt that two colonies in this collection, the 

 one growing inside the lip of a univalve shell, the other on 

 the base of a specimen of Alcyonidium gelatinosura, belong to 

 this species ; if so, however, Mr. Busk's figure and those 

 given by Smitt ((Efv. Akad. Forh. 1867, pi. xx. figs. 24, 25, 

 27) need supplementing by a more detailed one. 



In these specimens the zooecia are large, distinct, with 

 raised edge, oval, or very commonly smaller at the distal than 

 at the proximal end ; the area has a very slightly projecting 

 calcareous rim, which is minutely fimbriated. On the edge, 

 at each side of the mouth, are two pointed avicularia on 

 short peduncles, the apices projecting upwards and back- 

 wards. One, two, or three pairs of spines occur below these 

 avicularia on the edge. The ooecia are remarkable for singu- 

 lar modifications of form. In the simplest form they are 

 oval, of medium size, smooth, with the exception of some 

 striffi radiating up and backwards from the mouth ; the mouth 

 is provided with a very slightly upwardly-projecting lip. In 

 the next stage a longitudinal ridge runs down the surface of 

 the ooecium. In the next the rims of the neighbouring cells, 

 of which the lateral ones touch the ooecium, while the posterior 

 one is some distance off", surround it like a frame, and become 

 prominent, and at the same time a horizontal ridge runs across 

 its surface and joins the two prominent lateral walls ; the 

 upper lip of the mouth at the same time becomes much deve- 

 loped. Finally the anterior portion of the ooecium, viz. that 

 enclosed between the lateral rims, the hoi'izontal ridge, and 

 the lip of the mouth, becomes depressed, so that the whole 

 space above the cell appears to be occupied by two rectangular 

 arese, and the ooecium itself has become much less convex 

 than at first, and is almost entirely disguised by the structures 

 added to it. The cells radiate regularly from the centre. 



Homologies of Parts of the Ooecium. — This ooecium is one of 

 the most complicated in external characters which occur in 

 the Chilostomata ; and it would be interesting if the morpho- 

 logical significance of its difi'erent parts could be determined. 

 The occurrence of several of what appear to be stages of its 

 progressive development in one specimen seems to afford some 

 opportunity for making deductions on the subject. Probably 

 the large front depression of the last stage, with its surrounding- 

 raised margin, represents a rudimentary avicularium, as such is 



