REPORT ON THE ACTINIARIA. 95 



peculiar mode of development, whilst the accessory septa, which are paired from the 

 beginning, are still wanting. 



The constitution of the septa in Ilalcampa clavus shows further peculiarities worthy 

 of notice, which seem to me to indicate its relation to the Edwardsise. As I was preparing 

 a series of sections through the one half of the physa of the larger specimen, it struck me 

 that three septa (including the pair of directive septa) were not so strong as the other 

 septa, inasmuch as their longitudinal muscular cords became sooner indistinct (PI. XIII. 

 fig. 7). In the second smaller Halcanypa, in which I was able to make sections through 

 the entire body, four septa were somewhat smaller than the eight others ; and, finally, 

 Strcthill Wright has described a parasitic Ilalcampa living on Medusas {Halcampa fultoni) , 

 in which we can distinguish four stronger and eight weaker septa (Ann. and Mag. Nat. 

 Hist., ser. iii. vol. viii. p. 133, 18G1). All this shows that an unequal development of the 

 septa, and, consequently, a difference in their morphological value, is not unusual in Ilal- 

 campa. If we assume that the eight stronger septa are homologous with the septa of 

 Edwardsia, whilst the four other septa are new formations, then the genus Ilalcampa 

 would present us with transition forms between the Edwardsise and the Hexactiniae. 



I shall not discuss the point in question further, but I wish to draw particular 

 attention to the importance of a detailed investigation of the Ilyanthidae for a phylo- 

 genetic study of the Actiniaria. I am of opinion that an investigation of the position of 

 septa, extended not only over the mature animals, but also over the larvae, would 

 furnish us with very interesting explanations as to the manner in which the paired 

 arrangement of the septa has been developed among the Actiniaria. Of course a mere 

 enumeration of the septa would not suffice, but it would be necessary to lay down definite 

 characters for the determination of the septa newly formed in the Ilyanthidae, with special 

 reference to the distribution of the muscles and the relations of position depending 

 upon it. 



Reproductive organs were present in all the septa; ovaries in the larger of the 

 two specimens examined, testes in the smaller ; they lay below the oesophagus, inwards 

 from the longitudinal muscles. The ovaries were admirably preserved, so that I availed 

 myself of the opportunity to make a more detailed examination of the origin of the ovicells 

 and the structure of the filamental apparatus. The youngest ova are again portions of the 

 epithelium (PI. XII. fig. 11), and become surrounded very gradually by the supporting 

 lamella ; if the latter be strongly coloured, we see from ova of considerable size, such as 

 that given in fig. 11, that they are not yet entirely surrounded by the supporting 

 lamella, but that the interior of the follicle of the ovum still communicates with the 

 epithelium by means of a wide, roundish opening. A fine hatching is visible on that 

 portion of the ovum which closes the opening as though fine filaments were present 

 on the surface ; these are either processes of the ovum itself, which serve to connect 

 it with the epithelium, or they are the bases of the epithelial cells. This point 



