L— MORPHOLOGICAL OBSERVATIONS. 



In the class of Calcarea, Prof. Haeckel distinguishes three families — Ascones, Sycones, 

 and Leucones, characterising them according to the properties of their canal system. In 

 each family he establishes seven genera, taking the character of the spicules (whether 

 triradiate, quadriradiate, or acerate) as the generic character, seven combinations being 

 thus possible. The form of the spicules is reserved for the establishment of specific 

 characters. The classification constructed upon these principles Prof. Haeckel calls 

 " natural," 1 and puts it in opposition to his former classification published in the year 

 1869.' 2 It cannot be denied that in comparison with the system of the Prodromus, 

 the arrangement proposed in the Monograph is a great advance ; the arrangement of the 

 Monograph, although still rather artificial, is incomparably more natural than that of the 

 Prodromus, and shows that its author had made great progress in the recognition of 

 the organisation of the calcareous sponges. There is, however, a great difference between 

 a more natural and a really natural system. A natural system is the last link of a long 

 chain of investigations, it is the crown of all former studies, it becomes possible only 

 when the majority of the representatives of a group of animals has been examined ami 

 described. The very fact that of the thirty species brought home by the Challenger 

 Expedition, twenty -three present quite new forms, proves clearly how few Calcarea we 

 know, and how very many forms are still to be discovered. And therefore, till the right 

 time comes for making a summary of our knowledge, nothing but attempts at a natural 

 arrangement can be given. The system of Prof. Hasckel is no essay. Having 

 founded his genera upon all the possible combinations of the three kinds of spicules, 

 he thereby restricted the number of genera for ever, and, even though he had been 

 thoroughly justified in this by the forms he had for examination, he would still have 

 been premature in classifying the Calcarea in the manner he did. But it is sufficient 

 to peruse the Monograph attentively in order to find that the justification just mentioned 

 did not exist. For instance, characterising one species of Leucones — Leucetta curticata — 

 Prof. Hseckel writes as follows: — " Leucetta corticata is one of the most peculiar Leucones, 

 and possesses a near ally only in Leucaltis clathria." s The same, mutatis mutandis, is said 



1 Kalkschwamme, Bd. i. p. 79. 



2 Prodromus ernes Systems der Kalkschvv.imuii, Jeiuische Zdtschr., 1! 1. v. pp. 236-234, 1870. 



3 Kalk&chwamnie, Bd. ii. p 130. 



