48 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Oceciii of the ordinary typo are entirely absent, and their function 

 appears to be performed by special cells which differ in form from 

 the others. "When decalcified these occcial cells appear as thick- 

 valled sacs, containing in most cases an ovoid mass, which resembles 

 the contents of an ordinary ooecinni,aud like these is almost certainly 

 embryonal. Mr. Busk has further made the important observation 

 that in some of them there is lodged instead of this mass a polypide 

 similar to those inhabiting the zooecial cells, and he concludes that 

 the embryonal mass is derived from a polypide, which it finally 

 rejilaces. Among other peculiarities of the Adeonete is one which, 

 notwithstanding its apparent triviality, derives importance from its 

 constancy. This consists in the universal presence of a projecting 

 point at each end of the base in the avicularian mandibles, both large 

 and small. In doubtful fragments this character alone will often 

 indicate the aflinities of the species. 



In a large projiortiou of the diagnoses the author has had recourse 

 to the chitinous elements of the skeleton. These are the so-termed 

 opercula or oral valves, and the chitinous parts of the avicularia and 

 vibracula ; and a very large number of accurately executed outlines are 

 given in order to show the various forms assumed by these elements 

 in the different species. The employment of the chitinous elements in 

 the classification and descriptive zoology of the Polyzoa is due entirely 

 to Mr. Busk, who has convinced himself that " their value for these 

 purposes cannot be overrated, while their importance extends far 

 beyond the mere distinction of genera and species." 



The descriptions of the species are of course necessarily confined 

 to the hard parts, whether calcareous or chitinous, for, except in 

 living examples, it is rarely possible to determine any facts of 

 importance regarding the soft parts of the colony. The author, how- 

 ever, gives two highly instructive figures of the avicularia of Bicel- 

 laria pectogemma, in which the muscular ajjparatus and other soft 

 parts of these curious and still enigmatical bodies are clearly and 

 beautifully represented. In one of his figures of Carhasea moseleyi 

 also — a form in which the calcareous walls are quite transparent — 

 there is a very interesting view of the polypides in the interior of 

 their cells. 



The distribution of the species, geographical and bathymetrical, 

 finds a prominent place in the Report. One of the most unexpected facts 

 brought out is the very wide bathymetrical range enjoyed by certain 

 species. Thus Crihrilina monoceras is one of the four species brought 

 up from 3125 fathoms in the North Pacific, while the same species 

 was obtained from 1.325 fathoms in the South Pacific, from 69 fathoms 

 in the South Indian or Kerguelen region, from 55 fathoms in the 

 South Atlantic, and from 35 fathoms in the Australian region. This 

 striking difference in the depths inhabited by one and the same species 

 is, however, exceptional ; and so is the wide range of geographical 

 distribution which is here presented by a species occurring at great 

 depths. The study of the bathymetrical distribution of the ' Chal- 

 lenger ' Polyzoa shows that " the extent of geographical distribution 

 is to a considerable degree correlative with the bathymetrical, the 



