xlvi THE VOYAGE OF H.M.S. CHALLENGEE. 



Owing to the shrinking and distortion of the chambers from the action of the spirit 

 it is not easy to arrive at very certain conclusions either as to their form or size ; 

 probably in many cases in which a chamber now appears to be oval this shape is chiefly due 

 to lateral pressure ; and it is noteworthy in this connection that the elongated form is most 

 commonly to be observed in corticate sponges, which, owing to the presence of the fibrous 

 tissue, probably contract more strongly when put into spirit than the non-corticate species. 



Within the species the size of the chambers appears usually to be very fairly constant, 

 but the above table seems to indicate that it is not likely to prove of much value for 

 systematic purposes, except perhaps occasionally in the distinction of species or at the 

 most of genera. 



Mr. Carter^ has already pointed out that the diameter of the chambers ("ampul- 

 laceous sacs") is about l-600th of an inch ( = 0'042 mm.)* in the siliceous sponges, and 

 also that in this group they are for the most part globular, results which agree very well 

 with those above given by us. 



As a rule the chambers in the Monaxonida are embedded in trabeculae of mesodermal 

 tissue which separate the ultimate inhalent lacunae from the ultimate exhalent lacunae, 

 and they open into the latter by wide mouths {e.g., Esiyerella ofiurrayi, PI. XLVIII. fig. 

 2d ; Axinella (?) paradoxa, PI. XLIX. fig. 2 ; Latrunculia apicalis, PI. LI. fig. 1«). In 

 Stylocordyla stipitata, var. globosa, we have, however, at any rate occasionally, narrow 

 exhalent canaliculi leading away from the flagellated chambers (cf. PI. L. fig. la), a 

 condition which appears to be much more distinctly pronounced in Polymastia 

 ( Weberella) bursa, as described and figured by Vosmaer.^ 



Hansen have suggested that they are absent. Vosmaer, speaking of Pliakellia howerhanki, expresses himself very 

 guardedly : — "Also in Phakellia howerhanki I could not detect ciliated chambers. As long as I have not studied 

 PhakelUee which I have preserved myself, being sure that they were living in the moment they came in alcohol, I will 

 not pretend that they really do not exist. But it may be suggested here as a possible fact, that those thin fan- 

 shaped sponges are destitute of them because they do not want them. Every good section shows us that the water can 

 flow through and through the body, the natural movement of the water being probably sufficient for bringing new 

 living material to the sponge (fig. 12)" (Sponges of the "Willem Barents" Expedition, 1880-81, p. 24, 1885). The 

 idea that the water can flow right through from side to side, as indicated here and in Vosmaer's figure, must have arisen 

 from the badness rather than the goodness of the sections (cf. PI. XLIX. fig. 3). Hansen expresses himself with much 

 more confidence concerning his researches on the subject : — " Nach diesen Resultaten der Untersuchung muss man 

 annehmen, dass das Wasser durch die Kanale stromt ohne durch Flimmerbewegung fortgeleitet zu werden ; die 

 Oefi'nungen an der Oberflache kann man demnach als Ostien oder Poren bezeichnen je nach Belieben ; sie functionieren 

 wahrscheinlich als beides zugleich. Da die Phakellien meistens diinne Flatten bilden, die fiist wie ein Sieb durch- 

 lochert sind, wird es kaum schwierig zu verstehen, dass ihnen Nahrung zugefiihrt werden kann einfach durch die Wasser- 

 strbmung ohne dass es ndthig ware diese Stromung durch besondere Einrichtungen zu fordem." (Bergens Museums 

 Aarsberetning for 1885, Bergen, 1886). And this, notwithstanding the fact that Hansen has "keine Schwierigkeit 

 gehabt frisches Material zu beschaffen." The flagellated chambers in Phakellia ventilabrum, var. connexiva are perfectly 

 distinct and closely crowded together {vide PL XLIX. fig. 3), and there cannot be the slightest doubt that they are present 

 also in other species of the genus. 



' Ann. and Mag. Nat. Hist, ser. 4, vol. xvi. p. 22. 



2 Not 0'42 mm. as given by Vosmaer (Bronn's Klass. u. Ordnung. d. Thierreichs, Porifera, p. 129), which is 

 probably a misprint. 



3 Sponges of the " Willem Barents " Expedition, 1880-81, p. IV, pL iii. fig. 9. 



