900 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the soft parts of this beautiful and highly evolved form has hitherto 

 appeared. Professor F. E. Schulze has now undertaken this task, 

 having had at his disposal for the purpose the specially prepared 

 specimens brought to England by the ' Challenger.' Of these 

 specimens those preserved simply in absolute alcohol were alone 

 available for satisfactory histological examination. 



The soft tissues are pale yellowish-grey in colour, are small in 

 quantity, and constitute a meshwork of fibres or membranes. The 

 lateral walls are penetrated by numerous circular " wall-openings " 

 about 2 mm. in diameter, arranged in spiral rows, and maintaining a 

 constant communication between the interior of the sponge and the 

 surrounding water. There are, besides, openings on the inner surface 

 which lead into the body-wall and lie in the angular intervals of the 

 skeleton, viz. (1) larger openings underlying the prominent outside 

 ridges, either single or two or three in each interval ; (2) smaller 

 openings, underlying an outside boss, several in each such area ; both 

 sets are excretory in function. The wall is made up of — not con- 

 sidering the silicious elements — a skin which stretches between the 

 radially directed main axes of the large six-rayed spicules to which 

 the floricomo-hexradiates (" floricomes " of Schulze) are attached ; 

 this skin is pierced by the dermal pores, which are numerous and 

 communicate with subdermal spaces, formed of a lacunar network. 

 At the inner side of the latter is found a system of ciliated chambers ; 

 these are large cylindrical sacs, circular in transverse section, with a 

 coecal rounded termination, average dimensions -^q by ^\ mm. ; they 

 lead by circular apertures into digitate excretory caeca, iV *^ i Tam. 

 in diameter, which lead either into canals which open at once into the 

 interior of the sponge at the large openings (1) above mentioned, or 

 unite to form still larger canals with openings 3 mm. in diameter ; 

 the canals in those parts of the wall which lie between the large 

 ridges are much shorter and open directly to the interior by the 

 numerous small openings (2) above mentioned. There are no ciliated 

 chambers in the tissue immediately surrounding the wall-openings. 

 The regular external oscular openings are those of the cribriform plate, 

 not the wall ojienings ; the plate is thinly covered by soft matter 

 containing ciliated chambers at its outer side. The root tuft of fibres 

 appears to be quite destitute of soft tissues. 



With regard to the histology, three body-layers are distinguishable ; 

 the ectoderm covers the external surface and lines the inhalent spaces ; 

 its constituent cells were not distinctly made out, but their existence 

 is indicated by the presence of small round nuclei, regularly dis- 

 tributed. That part of the endoderm which lines the excretory canals 

 and the general internal surface of the sponge closely resembles the 

 ectoderm ; that lining the ciliated chambers has a very ditt'erent 

 character, although the structure of the lining epithelium was not 

 fully made out ; but here the lining cells were observed as ag- 

 gregated roundish masses, each containing a small round nucleus 

 with strongly refractive nucleolus, like that usual in collar-cells of 

 other sponges ; no " collars " or cilia could be detected ; the most 

 remarkable point determined in the chambers was a reticulate arrange- 



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