REPORT ON THE KERATOSA. 13 



opinion, in spite of objections made by Dr. Marshall,^ has also been adopted by 

 Dr. Vosmaer." Prof. F. E. Scliulze is indeed the most eminent spongiologist of the 

 present time ; Dr. Vosmaer is his pupil, and since I have entirely different ideas on the 

 matter, I must submit it to a most careful examination. There are three questions to 

 ■ be answered, namely, first, whether the filaments form a constituent part of the organism 

 of certain sponges or are independent organisms ? second, if they are independent organisms 

 are they to be regarded as parasites ? and third, if so, is their presence to be used as a 

 character of systematic consequence ? 



Do the filaments stand in an intimate connection with the sponge organism, or are 

 they independent beings ? We have seen that this question has been answered in 

 the negative by numerous investigators. This negative answer has, however, had either 

 no foundation in fact, or only an ambiguous one, till F. E. Schulze's paper on Hircinia 

 appeared. What we read in the Icones histologicse of Kolliker (p. 49) is to be regarded 

 merely as a simple supposition ; in the papers of Carter and Hyatt we have indeed 

 to deal with a conviction, but this conviction is far from being contagious. Hyatt states' 

 nothing more than that the examination of filaments by Dr. Farlow led to no definite 

 results as to their nature. Carter wishes to prove their parasitic nature by the fact 

 that he did find filaments in many non-Keratosa, and again missed them in notorious 

 Hircinida3 such as Hircinia campana. It may be said, however, that, as to the latter 

 argument, the sponges in question have accordingly not been Hircinidae, and as to 

 the former one, that it is also of no decisive nature, the reliability of the observations 

 upon the point being still questionable. This has been pointed out by F. E. Schuke in 

 his above-mentioned paper (p. 33), and there has been no answer on the part of Mr. 

 Carter. The discovery of 0. Schmidt that the filaments, which by their shape vividly 

 recall skipping-ropes, are quite free at both extremities, proved that they had nothing 

 to do with the skeleton, but did not prove their independence of the sponge organism 

 in general. This latter has been made obvious liy Schulze, who made out the struc- 

 ture of sponges characterised by the presence of filaments, and found that anatomically 

 and histologically they do not differ from sponges which like Euspongia have never 

 been found with filaments. To this statement I ascribe the highest importance. If 

 the filaments have nothing to do with the skeleton, and if again there exist no 

 deviations in histological structure of the corresponding sponges, which deviations, 

 according to the law of correlation, ought to be expected, provided that filaments 

 form a constituent part of their body, there are no grounds to consider them to be 

 part of it. Whether they are algfe or fungi still remains questionable, but their 

 nature as independent organisms is, I think, now clearly established. Schulze himself is 

 also of this opinion, although, with his usual prudence, he states it rather conditionally. 

 Notwithstanding, he is still inclined to ascribe to the presence of filaments a high sys- 

 tematic significance ; he appeals to an analogous instance in the vegetable kingdom. He 



' Zeitschr.f. loiss. Zool, BJ. xxxv. p. 112. - On Velinea gracilis, p. 445. ^ Revision, &c., part ii. p. 546. 



