670 SUMMARY OF CURRENT RESEARCHES RELATING TO 



covered by a series of cuticular formations showing no distinction into 

 plates and scales ; the capitular plates have arisen by a specialisation of 

 these primitive scales, and are therefore equivalent to modified and elabo- 

 rated peduncular scales ; on the other hand, in those Cirripedes which 

 have soft peduncles, the primitive scales have in that region undergone 

 gradual degeneration, and may be represented only by little specks of lime. 

 In a later communication* the author discusses the relation of the 

 pedunculated and sessile Cirripedes, as indicated by the hard parts. He- 

 believes that the relation is best indicated in the following scheme : — 



&c. 

 Lepas 

 Pollicipes 

 Scalpellum 

 Plumalites. Lot icula 



Tubicinella ? 



GhihamalvA 



fialanus 



&c. 



The genera Plumulites and Loricula represent the point of origin of 

 both sessile and pedunculated forms, the base of the Balanidra, which 

 was at first membranous and then calcareous, being formed by an 

 increase in size of the zone of fixation in the Lepadidae. The " rampart " 

 of the Balanidae has arisen from a fusion of peduncular scales ; the 

 operculum is equivalent to the terga and scuta of the Lepadidae. The 

 genus Tubicinella, save for its enlarged base, may represent the first 

 stage in the development of the Balanid type, the successive stages 

 showing increasing proliferation and coalescence of the peduncular 

 scales, while the opercular valves remain unaltered or even atrophy. 

 In the Lepadid type, on the other hand, the peduncular scales have 

 gradually diminished and the capitular plates have attained a higher 

 degree of development. 



A further paper f suggests a modified classification of the Thoracica, 

 the salient features of which may be indicated as follows : — 



Sub-order Lepadidae (Pedunculated Cirripedes). 



Family (1 ) Polyaspidas (scales on peduncle). 

 „ (2) Pentaspidae (no scales on peduncle). 

 „ (3 1 Tetraspidae ,, „ 



„ (4) Anaspidae „ „ 



* Tom. cit., pp. 140-7. t Tom. cit., pp. 152-7. 



