ITS SPECIES AND OVICELLS. 129 



as so much work is in the dark, for a suitable piece cannot be examined and 

 chosen as in transparent species. However, it is to be hoped that further 

 sections will elucidate some points still uncertain, and that we shall learn 

 whether these polypides must be compared with those of Tubucellaria. 



A more detailed examination of the ovicells of the Bryozoa is likely to 

 reveal many new points : for instance, I find that the ovicell of Thalamo- 

 porella Rozierii, And., is double, and contains a larva in each division ; also, 

 the ovicell of Idmonea radians is compound, containing a group of larva3 in 

 each of the four to six divisions. 



It seems much the simplest plan to retain the old name " ovicell " as a 

 general term, and then, instead of giving a special name for each kind of 

 ovicell, to distinguish them by saying that the ovicell is a gonocyst, or 

 that it is peristomial, and so forth. 



TUBUCELLAEIA CEREOIDES {ElUs Sj- Solandev). (Plate 15. figs. 8, 9, 15, 16.) 



Cellaria cereoides, Ellis «fe Solaiider, Zoophytes, p. 26, pi. 6. figs. B, C, D, E, 1786. See 

 Miss Jelly's Catalogue, under opuntioides, for synonyms, tliough Vincularia fi-agilis of 

 Defiance and of Blainville is not Tubucellaria, but add : — 



Vijicidaria fragilis, Michelin, Icon. Zooph. p. 175, pi. 46. fig. 21, 1840. 



Tubucellaria cereoides & vai'., MacGillivray, Tert, Polyzoa Victoria, p. 105, pi. 4. fig. 1, 

 1895. 



Tubucellaria opuntioides, Calvet, " Bry. Mar. des Cotes de Corse," Trav. Inst, de Zool. de 

 Montpellier, ser. 2, mem. 12, p. 11, 1902. 



After Busk in the 'Challenger' Report had separated T. cereoides, Ell. & Sol., 

 and T. opuntioides, Pallas, I followed him in using the latter name, although 

 expressing my doubts as to the correctness of this separation. A further 

 study of Busk's and of other specimens in the British Museum has convinced 

 me that he was not right in the separation which he made ; and now having 

 another species, T. fusiformis, d'Orb., with which Pallas's description agrees" 

 much better, we must certainly retain Ellis and Sollander's name, which has 

 so long been in use. 



Busk's specimens of T. opuntioides are all from the John Adams Bank, 

 N. Atlantic, and at first I thought that there might be differences of sufficient 

 importance for separation, especially in the ridge at the base of the peristome, 

 but having been permitted to make some preparations for the British Museum 

 of the " opuntioides,^'' I now consider that, so far as there are available 

 characters, there is no material difference. In Tuhucellaria the divisional wall 

 is continued under the peristome (figs. 1, 8, 10), and in the John Adams Bank 

 specimens this could hardly be made out until the covering membrane was 

 removed. The specimen is less stout than is usual in the, Mediterranean 

 forms, and there are no large open pores round the peristome, though at the 

 same time it is identical with some Mediterranean forms. 



We thus have the Tubucellaria cereoides in its simplest form, with the 

 peristomial ridge not very prominent, in the Atlantic ; it occurs in its most 



