BY R. J. TILLYARD. 



more swollen or sausage-shaped. In D. euphcedides Tillyard, the 

 gills are shorter still, 8'5-9 mm. long, shaggy, shortly pointed, 

 and tensely swollen. 



(ii.) The Constricted Saccns (Text-fig. 14). This very remark- 

 able form of gill is found in the genera Neosticta and Nososticta 

 among the Protonemn^tct. Both larvae are rock-dwellers, with 

 habits closely similar to those of Diphlebia, except that they are 

 often found on the sides of larger rocks in deep, still pools. 

 These larvse can move fairly quickly underwater, and their gills 

 are certainly not as cumbrous as those of Diphlebia. 



The shape of the gill may be 

 roughly described as that of a 

 rather short candle surmounted b}- 

 a flame, the basal joint represent- 

 ing the candle, the distal joint the 

 flame. The constriction between 

 the two joints is very strongly 

 marked, and is only just sufliciently 

 wide to allow of the passage of the 

 main trachete and the blood-canals. 

 The cuticle is covered everywhere 

 with small, scattered hairs, which 

 become longer and more abundant 

 upon the distal end of the basal 

 joint, and also over the whole of the distal joint. As in the 

 gills of Diphlebia, the cuticle is quite clear and unpigmented. 

 The hypodermal pigment, unlike that of Diphlebia, is not dis- 

 tributed equally all over the gill, but is chiefly confined to three 

 transverse zones, viz., around the base of the gill, around the 

 distal third of the basal joint, and upon all except the extreme 

 base and tip of the distal joint. 'J'his is well shown in Plate i., 

 fig. 6. The hypodermis is of about the same thickness, 4/y., as in 

 Diphlebia, and its nuclei are also of the same size as in that 

 genus. The cuticle, however, is only 5// in thickness, though 

 otherwise closely resembling that of Diphlebia in structure. 



Internally, the structure of the basal joint of the gill resembles 

 very closely the structure of the gill of Diphlebia, except that 



*Gills of Neofiticta cariesceiis Tillyard, in natural position, dorsal view;( x 5). 



Text-fig. 14.* 



