TRANSACTIONS OF SECTION D. 



701 



7. New Form of Apjpendicularian ' Haus.' Bij Geo. Swainsom, F.L.8. 



' Hans ' was the name given by the Russian naturalist, Von Mertens, to the 

 large transparent enveloi^e or sac so rapidly formed by the Appendicularia, Oiko^ 

 pleiira cophocerca, as a secretion from the ectoderm which he met with ia the arctic 

 seas in 1829. He asserted that this envelope was an organ of respiration, consist- 

 ino' of a regular network of vessels, in which the circulation of blood-corpuscles 

 was evident. This was greatly doubted by Professor Huxley as being, if true, 

 * \inique and startling,' and constant search was made for other specimens but with- 

 out success until 1858, when Professor Allman captured another and very different 

 form of 'Haus' in the Clyde.* Since then Von Mertens' species has been seen 

 and described by Fol.- „ , -, 



Fishino- off St. Anne's Pier (Lancashire) with a small bottle attached to my 

 surface net in June, 1890, I captured a new form of this ' Haus ' (see dra-^ving 

 annexed), but unfortunately lost it before I had time to properly examine it. 



Tiul- of 

 af^ax/ixjaxJxufia,' 



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''^UovJX 



mm tw^ 



There was no doubt about the tunicate body of the Appendicularia with its 

 ' stigmata,' &c. ; but the gelatinous envelope or sac appeared to have two whips oi- 

 fan-like organs. Professor llerdman on seeing my drawing at once suggested) 

 these were probably the optical expression of the tail of the Appendicularia tui-ned 

 upon itself. . . , 



This diaphanous sac was shaped very like a bishop's mitre and into it the salt 

 water was conr^tantly being driven by the lashing whips, and I saw an oval body 

 ejected from it, which I now believe to have been a fertilised ovum. 



Fortunately on the third of this present August I was successful in capturing a 

 second specimen, brought along by a strong tidal current from the IVorth-west 

 Atlantic. On examining it in a watch-glass I found Dr. Herdman was quite 

 right, for the tail of the Appendicularia formed the upper side of the mouth of the 

 sac, while the other side of the opening was made of the thickened and folded edge 

 of the gelatinous membrane which was connected with and secreted by the posterior 

 part of the Appendicularia. 



The constant lashing of the tail was responded to by a co-ordinate muscular 

 action in this thickened membrane, and the whole gelatinous mass was carried 

 about through the surrounding water by these continuous vibrations. Although 

 constructed for a similar purpose, the size and form of the ' Haus ' m my specimens 

 differed very much from both Allman's and Von Mertens', being about half the 

 size and possessing neither the ' double fans ' of Allman's nor the 'horns ' of Von. 

 Mertens', and the bifurcation of the sac being most distinct and noticeable. 



' Quarterly Journal of Microscopical Science, \?)iJO. 



* ' Etudes sur les Appendiculaires du Detroit de Messiue ' in Mtm. Soc. I /njf. 

 Hiit. Geneve, vol. xxi. 



