640 
THE VOYAGE OF H.M.S. CHALLENGER. 
Barrois’s Embryologie de quelques Sponges de la Manclie and from Vosmaer’s paper on 
Leucandra aspera, proved that, contrary to Haeckel’s assertions, the Leucones seem to 
be more closely allied to the Sycones than to the Ascones. But all these statements, 
valuable and important as they were from a morphological point of view, could not serve 
as a basis for a new arrangement of the group. They rendered every one still more 
conscious of the fact that Haeckel’s system is quite artificial, but they were too 
fragmentary for any systematic deductions. In order to construct for the group in 
question a new systematic edifice, not merely the study of a single species but the 
revision of a whole collection was indispensable, together with the simultaneous examina- 
tion of certain original forms examined and described by Haeckel. Such a collection 
had been made during the voyage of H.M.S. Challenger, and, further, thanks to the 
kindness of many naturalists, the author of the Report was enabled to obtain, for the 
purpose of comparison, most of the original Calcarea of interest and importance. The 
main results of the Report conducted under these very favourable circumstances are the 
following :■ — ■ 
“ The group of Calcarea is not to be subdivided directly into families as proposed by 
Haeckel, but primarily into two orders, namely (1) Homoccela, represented by the single 
family Asconidse, and characterised by a complete absence of differentiated flagellated 
chambers, the whole central cavity being covered with a continuous layer of flagellated 
cells ; and (2) Heterocoela, embracing the families Syconidse, Leuconidse, and 
Teichonidee, characterised by the fact that their central cavity, together with its clerivates, 
are coated partly with pavement epithelium (inhalent and exhalent canal system), partly 
with flagellated epithelium (flagellated chambers). 
“The above deduction is perhaps the most important in the Memoir, and therefore 
the communication here of the facts and arguments on which it is founded may not be 
superfluous. 
“The striking resemblance of the Asconidse to the phase of development of Calcarea 
known under the name of Olynthus was remarked long ago, and Haeckel as well as 
Vosmaer take the Olynthus in their phylogenetic speculations for the starting point, 
identifying it with the primitive Ascon representing the stock of the whole group of 
Calcarea. The deductions of Haeckel having been rejected by Vosmaer, those of 
Vosmaer — and particularly his flagellated epithelium theory — are now in their turn 
rejected by Dr. Polejaeff, who does not identify the Ascon with the Olynthus, this latter 
being, according to him, ‘ a neutral being, and the Ascon one of its modifications, the 
Sycon another.’ He states that £ an Olynthus may increase longitudinally without lateral 
growth, and in that case it will give origin to an Ascon.’ £ An Olynthus,’ he further 
suggests, £ may also grow in all directions in length as well as laterally,’ and on the 
ground of certain, so to speak, geometric arguments in connexion with others concerning 
the question as to what histological elements do in the Calcarea take in the nutritious 
