624 PEOrESSOE e. eay lankestee. 



to find some whicli were active and healthy, and to make some 

 observations of value with reference to (1) the existence of an 

 internal cartilaginoid skeleton, (2) the existence of a body- 

 cavity (denied by Sars), (3) the position and characters of the 

 testis and spermatozoa, (4) the nature of the axial chitinous 

 rod or blastophor of Allman, and (5) the general features of 

 the bud-production and constitution of the colony. I also 

 prepared some of the specimens by treatment with corrosive 

 sublimate, followed by alcohol; and of these, sections were 

 subsequently cut in my laboratory in London by my assistant, 

 Mr. A. G. Bourne, who accompanied me in my visit to Lervik 

 and rendered me much valuable aid. 



Assuming an acquaintance on the part of the reader with 

 the memoirs of Allman and Sars, I shall describe seriatim 

 the matters of interest which my observations have yielded. 



The TuBARiuM. 



In Plate XXXVII bis are drawn two specimens of 

 colonies of the Rhabdopleura obtained at Lervik. ■ They are 

 represented as magnified about three times linear. Both 

 specimens are attached to the test of Ascidia. The poly- 

 pides are withdrawn within the tubes which they secrete 

 and inhabit; consequently, we have practically before us 

 merely the branched tubular body forming the dwelling 

 or house of a Rhabdopleura colony. It seems undesirable 

 to apply the term "coenoecium" to this structure, or the 

 corresponding term " zocecium " to the units of which it is 

 composed, since those terms are applied in the description 

 of Polyzoa to structures which, though acting in a sense as 

 dwellings for the polypides, have a totally different origin and 

 morphological significance. The zooecium of an ordinary 

 Polyzoon is the locally thickened cuticle of the hinder part 

 (antitentacular region) of the polypides body to which it is 

 permanently adherent. The tubes of Rhabdopleura have no 

 such origin or attachment. Each tube is built up of a series 

 of rings, and each ring is separately secreted and added 



