I. INTRODUCTION. 



It has usually been supposed that the conditions under which marine animals occnr in 

 the Tropics are specially unfavourable for the growth of Polyzoa. Lamouroux *), speaking of 

 "Corallines", states that "il semble qu'une grande chaleur leur soit contraire"; while Ortmann 2 ) 

 remarks "Anderseits scheinen die Tropen eine Grenze für die Bryozoengebiete zu bilden"; and, 

 ten years later, Nordgaard 3 ) accepts the view that Polyzoa are rare in low latitudes. It has 

 indeed been clear for some time that the belief in the absence of Polyzoa from Tropical localities 

 is due merely to insufficiënt knowledge; but if any further proof were needed, the results of the 

 'Siboga' Expedition would be amply sufficiënt to disprove the view that Tropical conditions are 

 in any way antagonistic to the growth of Polyzoa. It may safely be asserted that, in Malay 

 waters at least, Polyzoa are present in large numbers, both of species and of individuals; and 

 that they occur from the littoral region down to the greatest depths investigated. The 'Siboga' 

 collection is far the richest that has at present been made in any Tropical region ; and it is 

 specially important in supplying information with regard to a district which had previously been 

 almost unknown. Further to the South, the Australian forms have received much attention 

 from Busk, MacGili.ivray, Hincks, Waters, Maplestone and others. Ortmann's paper, already 

 referred to, gives some information with regard to Japanese species. But with the exception of 

 papers by Hincks 4 ), Kirkpatrick 5 ), Miss Thornelv i! ) and Waters 7 ), little recent work has 

 been done on the marine Polyzoa of the Indo-Malay region, the importance of which from the 

 point of view of Geographical Distribution need not be emphasized. 



The official list of the localities at which specimens were collected during the voyage ot 

 the 'Siboga' includes 323 numbered Stations; and Polyzoa were found in about 134 of these. 

 In some cases the number of species obtained was very large. Thus in a single bottle from 

 Station 144 about 38 species were discovered. Although this is very much more than the 

 average number found, the process of sorting the material has been a very arduous one, 



1) Lamouroux, J. V. F., 1816, p. xxxm. 



2) Ortmann, A., 1889, p. 67. 



3) Nordgaard, O., 1900, "Norske Nordhavs-Exp.", XXVII, "Polyzoa", p. 27. 



4) Hincks, T., 1884, 1887. 



5) Kirkpatrick, R., 1888, 1890 1 , 1S90 2 . 



6) Thornely, I.. R., 1905, 1907, 1912. 



7) Waters, A. W., 1909, 1910, 1913, 1914. 



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SIP.OG A-EXPEDITIE XXVIII a. 



