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or with both these groups; with the total number of species, in each of the three groups, found 

 at each Station, foliowed by the total numbers of species of Polyzoa recorded. The table includes 

 those Stations which were most productive for Polyzoa in general ; the highest figures being 

 reached by Stat. 164, with 87 species, and Stations 77 and 273, with 65 species each. It will 

 be seen, by a simple process of subtraction, that the Cheilostomata are, in all these cases, in 

 excess — and usually largely in excess — of the other three groups together. The percentage 

 of Cyclostomata to the total number is, however, by no means uniform; ranging from 2.5 p.c. 

 at Stat. 274 (57 M.) to 29 p.c. at Stat. 105 (275 AL). This indicates that the conditions at the 

 various Stations are not equally favourable for the growth of Cyclostomata, although it is not 

 obvious why some are better than others. There is some reason to think that the Cyclostomata 

 are, on the average, better adapted for deep water than the Cheilostomata; and this is brought 

 out by the following Stations, not included in the table under consideration : — Stat. 1 19 (1901 M.), 

 with 50 p.c. of Cyclostomata (Cycl. 1, Cheil. 1); Stat. 97 (564 M.), with the same numbers; 

 Stat. 139 (397 M.), with 33.3 p.c. (Cycl. 1, Cheil. 2); and Stat. 59 (390 AL), with 25 p.c. 

 (Cycl. 2, Cheil. 6). But these numbers are too small to prove much; and it may be noted that 

 Stat. 251 (204 AL) yielded only 6.6 p.c. of Cyclostomata (Cycl. 1, Cheil. 14); while another 

 from shallow water (Stat. 315, o — 36 AL) gave the high proportion of 23 p.c. of Cyclostomata 

 (Cycl. 6, Cheil. 20). 



The table on p. 168 reveals certain marked differences between the Cyclostomata and the 

 Ctenostomata ; but this is not surprising, in view of the fact that the Cyclostomata are strongly 

 calcified, whereas the Ctenostomata are non-calcareous. The largest number of Cyclostomata (9) 

 was yielded by Stat. 105 (275 AL), where no Ctenostomata were found. Stat. 310(73 AI), similarly 

 characterised by the absence of Ctenostomes, provided 7 Cyclostomes. Stat. 240 (9 — 45 AL) 

 had 7 Cyclostomes and 2 Ctenostomes. In certain other cases the advantage was with the 

 Ctenostomes, as at Stat. 164, 32 AL (Cycl. 5, Cten. 9); Stat. 273, 13 AL (3,6); Stat. 71, 

 o — 32 AL (1,6); and Stat. 64, o — 32 AL (1,4). 



Cyclostomata occurred with Entoprocta in a larger number of Stations than with Cteno- 

 stomata; but it will be seen by the table on pp. 92 — 94 that a considerable proportion of the 

 records of Entoprocta are of species of Loxosoma which live on Rctcpora and other calcareous 

 Cheilostomes. The table on p. 168 shows that the various Stations are not equally favourable 

 for the occurrence of Cyclostomata and Entoprocta. This may be illustrated by Stat. 105, 275 AL 

 (Cycl. 9, Ent. 1), Stat. 282, 27— 54 AL (4,1), Stat. 274, 57 AL and Stat. 53, o— 36 AL (1,4) and 

 Stat. 164, 32 AL (5,5). Here again, no satisfactory explanation of the differences can be given. 



The majority of the Cyclostomes obtained came from shallow water. Two thirds ot the 

 records (65 out of a total of 98) were from depths less than 60 Aletres. Of the remaining 

 33 specimens, 14 were dredged in depths from 69 to 94 AL; 1 from 113 AL; and 18 trom 

 204 to 1901 AL The greatest depth (Stat. 119, 1901 AL) at which Cyclostomes were obtained 

 yielded only one species, Tubulipora cassiformis, obtained also at Stat. 156, 469 AL This may 

 accordingly be regarded as an abyssal form. Hornera spinigera was obtained in three deep 

 dredgings (Stations 97, 156, 105; 564, 469, 275 AL) but also at Stat. 117, So Aletres. The 

 single fragment of H. caespitosa came from Stat. 105, 275 AL; and the genus Hornera is thus 



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SIBOGA-EXPEDITIE XXVIII a. 22 



