22 THE VOYAGE OF H.M.S. CjHALLENGEE'. 



ill Rhabdopleura has also beeu carefully figured on a larger scale from life by Professor, 

 Lankester.' There are thus interesting points in analogy between the two forms in 

 regard to the polypide-stalk, but at the same time important structural difiierences. 



Professor Lankester again holds that the chitinous covering (his Caulotheca) of 

 certain parts of this region is the true homologue of the ccenoecium of an ordinary 

 Polyzoon, and there is something to be said in favour of such a view. As already 

 explained, however, I prefer to adhere to the term already in use, especially in the 

 present uncertainty in regard to the development of the types under consideration. 

 Nor do I fully share my friend's views concerning the "serious error" of confounding 

 the pedicle in the forms just mentioned with the funiculus of the Eupolyzoa. The 

 structural relations of the organ in the several forms no doubt differ, but the remarkable 

 analogy in regard to the budding shows that from the " vagrant protean funiculus " of 

 the Gymnolsematous Ectoprocta to the pedicle and soft stalk of Cephalodiscus and 

 Rhabdopleura there is at least one striking function carried out often on very similar 

 lines. Variations it is true occur, in which the endocyst is associated with the funiculus 

 in producing the buds in the marine Ectoprocta, but this does not affect the main point 

 at issue, but rather brings the analogy closer with such forms as Cephalodiscus. 



The pedicle on the other hand nearly resembles the stalk in Loxosoma. There is no 

 pedal gland, however, in CejAalodiscus. 



One of the most remarkable points of resemblance between Cej^halodiscus and 

 Balanoglossus is the occurrence of a pedicellate structure in the young of the latter 

 {Balanoglossus koicalevskii) as described by Mr. Bateson.'^ This organ presents itself on 

 the disappearance of the cilia as a small papilla, and is situated at the central part of the 

 posterior surface. Moreover, it is directed ventrally, just as the pedicle of Cephalodiscus 

 is, and, indeed, the general contour of the young form at this stage simulates the 

 condition in Cephalodiscus. This conical process serves as a sucker by which " the 

 animal can attach itself to foreign bodies sufficiently firmly to prevent being washed off 

 by a stream of water from a pipette. The anterior surface of the jjroboscis is also slightly 

 suctorial, and by thus fixing itself posteriorly, and extending the proboscis, it is able to 

 creep slowly about, somewhat in the manner of a leech." The organ " subsequently 

 attains a considerable size and is traversed by several wrinkles. It afterwards entirely 

 disappears, but as to its mode of disappearance I have no certain observations. It would 

 appear to occur very suddenly at the stage when the animal possesses seven to eight gill- 

 slits. I have found animals with eight gill-slits which possess this sucker, and also 

 animals of apparently the same age without it ; hence it may be inferred that it under- 

 goes a rapid atrophy at this point." Mr. Bateson further observes that similar suckers 

 occur as larval organs in Tunicata, Ganoids and Amphibia, but these fall far short, of the 



> Op. cit., pi. xl. fig. 12. 



^ Quart. Jmirn. Micr. Sci., Stud. Morpli. Lab. Univ. Camb., vol. iii. part i. p. 3, pi. i. figs. 1-4, 1886. 



