and their Relationsliip to the Corals. 119 



klucho's Guancha hlanca and. my Si/cometra comjyressa : these 

 two calcareous sponges occurnng in such various forms that 

 they seem to belong- sometimes to one and sometimes to anotlier 

 systematic group, and place systematists in the greatest diffi- 

 culty. In the following Prodromus of a system of the Calci- 

 spongire* I have been able to get over this difficulty only by 

 founding for them a special order — that of the Metrosyca. 



Giumcha hlanca (from the Canary Islands), in its most deve- 

 loped form, appears as a sjionge-stock ivhich hears on one and 

 the same cornius the mature forms of not fewer than four per- 

 fectly different genera .^ namely, Olynthus among the Monosyca 

 (form A of Miklucho), Leucosolenia (form B) and Tarrus 

 (form D) among the Polysyca, and Nardoa among the Coeno- 

 syea (Miklucho's form C). In the same way, the most deve- 

 loped form of the Norwegian Sycometra compressa appears as 

 a sponge-stock ivhich hears on one and the same cormus the ma- 

 ture forms even of eight different genera^ namely : — Sycarium 

 and Artynas, of the family Sycaridte ; Sycidium and Arty- 

 nium, of the family Sycodendrids ; Sycocystis and Artynella.^ 

 of the order Clistosyca; and Sycophyllum aii^ Artynophyllum, 

 of the order Cophosyca. But we must regard all these forms 

 united upon one stock as generically different, and not as mere 

 developmental stages of one species, inasmuch as each of them 

 is capable of reproduction, and bears about it in its developed 

 spores the convincing testimony of perfect maturity. In these 

 extremely remarkahle and important sponges the organic species 

 is to he ohserved as it loere " in statu nascenti.^^ 



The same is probably true of Sycarium rhopalodes from 

 Norway and Ute utriculus from Greenland, the latter described 

 by Oscar Schmidt, provided that the different forms of these 

 which I have ranged under the genera Sycarium, Artynas, 

 Sycocystis, and Artynella really manifest their specific matu- 

 rity by the possession of developed s])ores. 



If we return, in conclusion, to the relation between the 

 sponges and corals, and endeavour to establish artificially the 

 boundary between these two classes of animals, we find no- 

 thing essential except the higher degree of histological dif- 

 ferentiation in the corals, and especially their possession of 

 urticating cells. No sponge forms urticating organs in the cells 

 of its ectoderm, whilst these are present to a greater or less ex- 

 tent in all Acalephs (in all Corals, Hydromedusce, and Cteno- 

 phora without exception). It must be admitted that this his- 

 tological character is in itself very unimportant, and, in respect 

 of both its physiological and its morphological significance, is 

 but little adapted for the establishment of a sharji boundary 

 * A translation of this will appear in our next Number. 



