80 THE VOYAGE OF H.M.S. CHALLENGER. 



described by Prof. F. E. Schulze.^ Now, so far as the delicate construction of Eenieridse 

 is concerned, I can but confirm Dr. Vosmaer's statements as to the striking resemblance 

 of these Monactinellida with Euplectella. Prof. Schulze lays stress, however, also on the 

 fact that in Euplectella aspergillum—andi as he told me in HexactineUida in general — 

 the flagellated chambers are comparatively very large, and, in appearance, typically 

 pouch-shaped, recalling the radial tubes of the Sycouida3. In the species of Reniera I 

 had for examination, Reniera aquceductus, Reniera Jiligrana, Reniera semitubulosa, 

 Reniera Jibulata, and two or three Eenieridse not determined, I found then' flagellated 

 chambers to be always of roundish outline, therewith not larger, or at least but little 

 larger, than those of, e.g., Psammoclema vosmaeri. I would be, however, scarcely right 

 to lay stress on the contradiction in question, for, firstly, it is but too possible that there 

 are representatives of the genus Reniera with radial tube-like flagellated chambers, 

 and, secondly, the difi"erences between flagellated chambers of this kind and those 

 characterising my genus Psammoclema are of a thoroughly quantitative nature. At any 

 rate, it is clear that, so far as the Monactinellida, the most closely allied to the Keratosa, 

 are concerned, they are characterised by an arrangement of the canal-system of a more 

 primary character than that distinguishing the majority of the Keratosa. Is this not 

 an evident proof that they are to be regarded as palseontologically older sponges ? ^ I 

 think aU these circumstances together speak so decidedly for the supposition I am now 

 asserting that the matter can be regarded as scientifically proved. This deduction is 

 of great consequence, for under these conditions there are absolutely no grounds for 

 regarding the group of Keratosa as an order, i.e., a systematically higher unity than the 

 families Chahnidae, Eenieridse, &c., the more so as it is even impossible to say that 

 Keratosa are less closely connected with Chalinidse than these latter with the Eenieridse. 

 Of course the thorough absence of proper spicules in their skeletal fibres admits 

 of their very sharp diagnosis, while the diagnoses of Chalinidse and Eenieridse are 

 of a more conditional nature ; but who can warrant that the genus Spongelia is in 

 closer relationship with Euspongia tlian with Chalina? who can guarantee that 

 the relative characters distinguishing Spongelia from Euspongia, and concerning the 

 internal organisation of the soft parts, are of less importance than the equally quanti- 

 tative distinctions concerning the properties of the skeleton difi"erentiating the 



1 Trans. Roy. Soc. Edin., vol. xxxix., 1880, p. 661. 



2 The type of canal-system characterised hy an entire absence of special cameral canal iculi, and by clearness of 

 the ground-mass surroimding the flagellated chambers, can be regarded as chai-acteristic of ^Monactinellida in general. 

 Apart from the Renieridoe above mentioned, I can state this with respect to the following fonns I had the opportunity 

 of examining — Suberites domuncnla, N.; Espcria bauriana, O. S.; Myxilla rosacea, Lbn.; Myxilla vcneta, 0. S.; Baspailia 

 viminalis, O. S.; Acanthella acuta, 0. &.; Axinella polypoides, 0. S. On the contrary, the canal-system of the repre- 

 sentatives of the genus Papillina, 0. S. {Papillina stiberea, Papillina nigricans), is not less highly developed than 

 that of Aplysina aerophoba or Corticinm candelabrum ; but it must be added that the genus Papillina, although 

 undoubtedly closely allied to the genus Suberites, seems also through the genus Osculina, 0. S., to be stiU more closely 

 connected with the Chondrosidre, and may, together with these latter, represent a family palieontologically not less 

 recent than that of Ceraospongite. 



