EEPORT ON THE ANTTPATHARIA. 199 



entoderm of which is considerably thickened. A horizontal section of one of the trans- 

 verse mesenteries is shown in PL XV. fig. 2, which includes the whole breadth of the 

 mesentery. The upper oblique band of mesoglcea is that of the stomodseum ; that 

 below forms part of the body-wall. The mesoglcea of the mesentery does not appear to 

 consist here of the usual simple band, but towards the middle the band proceeding from 

 each extremity becomes broken up into a number of fibres, the limits of which could 

 not be observed. It appeal's clear, however, that the youngest ova are found in the 

 central portion of the mesentery adjoining the mesoglceal fibres. The germinal cells 

 appear to be derived from the entoderm, and various stages in their development are 

 indicated in the figure already referred to. As the ova increase in size they appear to 

 approach the surface of the entoderm. The tissue surrounding each of the large ova is 

 fibrous, but no definite mesogloeal capsule has been observed around them as in the case 

 of Antipathella contorta. 



Mesenterial filaments. — The majority of the specimens contain a few elongate and 

 simple ribbon -like mesenterial filaments about 0*7 mm. long, which reach halfway across 

 the coelenteron in transverse vertical sections. Each consists of a median band of 

 mesoglcea, on both sides of which a layer of entoderm occurs {cf. PL XIII. fig. 5). 

 The free margin on the other hand consists of a rounded cap of cells derived from the 

 storaodasal ectoderm. Other filaments are convoluted and branched. Occasionally one 

 of the short branches bears two lateral dilations which consist of entoderm cells. Such 

 lateral lobes have, however, been rarely observed, and certainly do not appear constant. 

 I am uncertain whether they should be regarded as homologous with the " Flimmer- 

 streifen" of the Actiniaria, or as accidental products due to the subdivision of a filament 

 near its apex. 



Parasites. — An interesting vermiform parasite has been met with on two occasions 

 in serial sagittal sections of Antipathella subpinnata. Unfortunately I am unable to 

 give a full description or suggest the affinities of the form in question, as my sections 

 do not include a whole individual in either case. The parasite is usually situated in 

 the lower part of the coelenteron between the base of the mesenteries, the body-wall, 

 and the skeletal sheath, and is usually confined to one side of the lumen. In cases 

 where it is in contact with the zooidal tissues the entoderm is considerably reduced. 

 The parasite occupies that part of the coelenteron which is usually filled with mesenterial 

 filaments. In both cases where the parasite is present the mesenterial filaments form a 

 convoluted mass pushed up into the lumen of the stomodseum, and one or two of the 

 filaments project freely beyond the mouth. This abnormality is probably due to the 

 presence of the parasite, and has not been observed in any other instances. One 

 specimen has been traced through 200 consecutive sections ( = circa 1/-2 mm.), which 

 include sections through two zooids and two interzooidal areas (ccenenchyma). In the 

 interzooidal areas the parasite completely fills the stolon-like lumen of the coelenteron. 



