THE SOLENOGASTRES OF THE SIBOGA-EXPEDITION 



BY 



H. F. NIERSTRASZ, 



Utrecht. 



W i t h s i x p 1 a t e s. 



I. INTRODUCTION. 



Until recently, not a single specimen of Solenogastres from the East-Indian Archipelago 

 was known. It was only in the year 1898 that Thiele gave a short diagnosis of two Australian 

 forms : one from Torres-straits, one from the N. \\\ coast of Australia (9). In this respect the 

 Siboga-expedition has been more fortunate than its predecessors. The expedition brought back 

 110 less than 65 specimens, a description of which follows here. 



All these specimens have been fixed in absolute alcohol, and preserved in 95 per cent 

 alcohol, a method, which I believe to be better than any other. And yet it is only of a few specimens 

 that the state of preservation may be called entirely satisfactory. The cause is not clifficult to fmd. 

 Only few forms lead a free life, and can undergo immediate fixation as soon as the contents of 

 dredge or trawl commence to be examined. Others however live in mud ; whenever a dredge filled 

 with mud came up, the mud had to be carefully examined and it often took a long time to find the 

 small Solenogastres ; during that time they had died and fixation only partly succeeded. The same 

 is the case with the numerous forms we find twisted around the branches of Gorg-onids. Owino- 

 to the large amount of work which a full dredge necessarily entails, the Solenogastres are only 

 detected when the Gorgonids are inspected. Consequently my sections are often of no value for 

 minute histological details. In the tollowing description I intend to lay stress upon the general 

 structure and to draw the attention to those characteristics, which are of importance for classification. 



Before cutting I decalcified the animals in a mixture of 3 per cent nitric acid in 70 per 

 cent alcohol. Though this renders the investigation of certain forms of spicula impossible this 

 method is to be recommended. If not decalcified the sections may be found to be very seriously 

 injured by fragments of larger spicula. After decalcification I stained the animals in toto with 



SIBOGA-EXI'EIUTIF. XI.VII. I 



i475I 



