29 



The only full-grown and well-preserved specimen was found in the Andamans 

 between the North and the South Sentinel Island in a depth of 403-439 m.=220- 

 240 fths. A fragment was procured in the Andaman Sea 13' 27' N., 93° 14' 

 30" E. in a depth of 741 m.=405 fths. 



My extensive investigations of numerous Japanese specimens of Hyalonema 

 aWne W. Marshall, including the type specimen in the Leyden Museum studied 

 by Marshall himself, have convinced me that this species is subject to great 

 variations, not only in the external form of the body but also in the distribution, 

 shape and size of some of the spicules, chiefly the dimensions and position of 

 the pentactine hypodermalia and the occurrence of mesamphidiscs. I now feel 

 certain that the Japanese sponges described by me in the " Challenger " Report 

 as Hyalonema apertum belong to Hijalonema affine W. Marshall, taken in the 

 wider sense I now give to it. The complete specimen, collected by the " Investi- 

 gator " in the Andaman Sea and previously also placed by me in the species 



& . . . . , . 



H. apertum, in no wise transgresses the limits of the variations met with m 

 U. a.ffitie, so that it must also be assigned to this species. Some of its peculiari- 

 ties, particularly the exceptionally strong development of its pentactine hypoder- 

 malia, render it desirable, however, to establish a distinct subspecies for its recep- 

 tion. The proof of its specific identity with H. affliie was given by me in the 

 paper " Ueber Hyalonema affine W. Marshall " (Sitzungsberichte der Gesellschaft 

 naturforschender Freunde in Berlin, 1899 pp. 112-129) cited above. 



In this paper I have also shown that the small specimens of Hyalonema, 

 which I originally considered as representatives of a distinct species and named 

 Hyalonema mcehrenthali, are young forms of the subspecies reticulatum F. B. Sch. 

 of Hyalonema affine, with full grown individuals of which they have been found 

 growing together. 



Twelve such young stages of varying size, which are on the whole pear- 

 shaped, have been found. Most of them have a circular transverse section, some 

 are laterally slightly compressed. The smallest specimen (pi. VII, f. 7) is 12, 

 most of them are 20-30 mm. long. The proportion of the maximum transverse 

 diameter, which lies a little above the middle, to the length, is usually 2:3. 



Everyone of these specimens has a more or less circular oscule, surrounded 

 by a smooth marginal border, on the upper end. In the largest this border is 

 particularly well-defined and sHghtly bent outward. On the whole, the size of 

 the oscule increases with the size of the sponge, but it is not exactly proportional 

 to it. The columella or central cone usually extends up to the aperture, but is 

 by no means always situated exactly axially. The radial septa, which extend 

 from it to the body-wall, typically four in number and vertical to each other, 

 are in accordance with this frequent excentricity of the columella also often 

 irregular, and there are often not exactly four main excurrent openings. Some- 



