J)v. M. Dybowski on Dosilia Stepanowli. 251 



cliitinizecl membrane, 0"004 millim. thick, the colour of which 

 is a darker or hg-hter horn-brown. The capsule passes directly 

 into the pore (vide infra) . The capsule is covered externally 

 with a thick layer, the coatinrj -layer ^ and tilled with the germ- 

 material. 



2. The Coating-layer (Belegschicht ; Vejdovsky's '' Paren- 

 chymschicht " * ; Carter's " spiculiterous layer "). 



The whole surface of the gemmula-capsule (with the ex- 

 ception of the pore) is covered (coated) with a layer 0*02G- 

 0'0'jO millim. thick, which exhibits the following parts : — ■ 

 a, the amphidisci ; i, the intermediate structure; and c, the 

 outer membrane [Oherltdutchen). 



Tiie amjjhidisci (as is also the case in some other Spon- 

 gilliie) are siliceous, spindle-shaped corpuscles (see Trav. Soc. 

 Nat. Charkow, pi. vii. fig. 1 h), which stand close to each 

 other perpendicular to the surface of the capsule. 



The shafts of the amphidisci are comparatively very long 

 and slender [vide infra) and have on the surface large, erect, 

 but rather scattered spines {ibid. fig. 1 h). Within the shaft 

 runs a canal furnished with organic matter, which, in calcined 

 preparations, appears as a black, opaque, longitudinal streak f . 



The margins of the terminal disks of the amphidisci, the 

 diameter of wdiicli is 0'0U8-0 012 millim., are deeply notched 

 and j'urnished with numerous small denticles. 



The am[)hidisci occur of two different forms, namely longer 

 (of 0*040 millim. in length and 0'002 millim. in thickness) 

 and shorter (of 0-024 millim. long and 0002-0-004 millim. 

 thick). The shorter amphidisci, which considerably exceed 

 the longer ones in number, are entirely enclosed within the 

 coating-layer, and do not extend beyond the outer membrane ; 

 the longer ones, on the contrary, protrude by their upper ends 

 from the coating-layer. 



When a gemmule is examined in transverse section it ap- 

 pears that a long amphidiscus follows from two to six shorter 

 ones ; sometimes two or three longer ones stand close together, 

 but they are always surrounded on all sides with shorter ones. 

 From this we must conclude that from one to three longer 



* The sponge-body itself is generally understood under the term 

 " pareucliyuia," and hence tlie name " coating-layer " {Beh'ijschiclit) 

 seems to me to be better and more suitable. The "coating-layer " con- 

 tains all sorts of " coating-corpuscles " (such as coating-spicules, amphi- 

 disci, &c.) which serve for the covering {Bcleyuiif/) of the gemmule; 

 and, further, the term " coating-spicules " {Behijnadeln) has been gene- 

 rally adopted. 



t By the ignition of the amphidisci the organic contents of the in- 

 terior canal become carbonized, and thus the otherwise invisible longi- 

 tudinal canal of the shaft comes distinctly into view. 



