24 GEORGE OSSIAN SARS. 



sea animals, compiled in 1868, as Halilophus mirabilis ^ (the 

 generic name taken from a certain resemblance of the 

 tentacular arms to the so-called lophophore of the fresh- 

 water Polyzoa). The next year appeared Allman's treatise 

 on Rhabdopleura, a new form of Polyzoa, from deep-sea 

 dredging in Shetland ;" and my father, as well as myself, at 

 once recognised in the species therein described and de- 

 lineated,- R- Normanni, a form closely agreeing with the 

 Halilophus mirabilis, but which evidently, from the form and 

 attachment of the polyzoarium, must belong to a diftereut 

 species from ours. Allman's communications concerning the 

 organisation of the animal show indeed, as will appear from 

 the sequel, many essential differences from what I have had 

 occasion to observe in our northern form ; so that if these 

 communications were in reality correct, there could scarcely 

 be any doubt that both forms were also generically distinct. 

 But the fact is that Allman has only had the opportunity of 

 examining specimens preserved in spirit ; and both my father 

 and myself know from experience how extremely difficult it 

 is to obtain results with specimens in this state, and what 

 imperfect and false notions may thus be formed of the 

 animaFs real structure. Taking this into consideration, we 

 may really be astonished that Allman has been able ta see so 

 much as he actually has seen, and that he has not misunder- 

 stood the animal's organisation in a greater degree than 

 appears from his description and delineations. Allman has 

 indeed seen in the Rhabdopleura a very aberrant form of 

 Polyzoa, but is far from having apprehended that the form is 

 abnormal in so high a degree as it has proved to be according 

 to investigations which I have executed with the utmost care 

 and minuteness. 



With respect to the method of examination, there is little 

 or no use in dissecting so small and fragile an object as the 

 animal of the Rhabdopleura, even if the finest imaginable 

 instruments are employed. It is, therefore, necessary to 

 study the animal entire, or at most, after separating the 

 individual animals from their cells or tubes, which, as will be 

 seen, may be done with the greatest ease in operating on the 

 living colony. In order to get a sharper and better view of 

 certain parts, I have found it very useful to effect a gentle 

 compression of the animal between two glass plates, so that 

 the pressure can be moderated at will. I cemented a thin 



^ 'Forsatte Beniaerkninger om det djriske Livs Udbredning i Uavets 

 Djbder,' p. 12. 



' ' Quarterly Journal of Microscopical Science,' vol. ix, 1869, pp. 57 — 03, 

 pi. 8. 



