REPORT ON THE CRUSTACEA MACRURA. 



455 



immediately after the completion of the change. He also kept several specimens and saw 

 them moult, assuming a form that was a little larger but similar in all respects, except 

 that the appendages of the jdeon were now present as small buds. Some of these were 

 kept until they .changed into a form strongly resembling a Sergestes. 



At this stage it appears that the observations of Willemoes Suhm are more distinctly 

 in the true line of development. 



"In August 1875, about 300 miles south of the Sandwich Islands, a young Crustacean 

 was captured which was believed to be a stage in the history of Leucifer, and which 

 Dr. Suhm named the Anqihion-stage. It measured as follows : — 



" Length, total, 



,, of rostrum, 



„ shield without rostrum, 



,, both together, 



pleon, 

 ,, telson, 



„ ophthalmopod, 



Diameter of carapace, 



2-67 mm. 



0-24 



0-63 



0-87 



1-3 



0-5 



0-31 



0-66 



" On the second maxilla I could not find a palpus in three specimens that I examined." 



The carapace has undergone a considerable change of form. The rostrum is long and 

 prominent, but the teeth on the posterior margin of the carapace both at the angles and 

 median fine have disappeared. But on the anterior margin of the carapace each angle 

 external to the ophthalmopoda is projected into a prominent tooth directed forwards, 

 whence the lateral margins are curved downwards and outwards, and then gradually 

 upwards and backwards to the postero-median dorsal surface of the pereion. 



In this stage the development corresponds with that known as the Acanthosoma-stage 

 of Sergestes, and corresponds with Sceletina of Dana. It differs, however, in having 

 the ophthalmopoda long, and, according to Suhm's measurement, one half the length 

 of the carapace, not including the rostrum. The ocellus is still visible as a spot of 

 pigment in the centre of the cerebral ganglia. 



The first pair of antennae consists of four joints sparsely fringed with hairs ; the first 

 joint is long, slender, and cylindrical, excepting for a small process on 

 the outer side near the base, the seat of the future acoustic organ ; 

 the second joint is less than half the length of the first and slightly 

 less in diameter ; the third is about the same length and thickness as 

 the second ; and the fourth joint consists of a small papilliform seg- 

 ment, which is the rudiment of the future flagellum. 



The second pair of antenna? is biramose, the inner being the primary branch of the 

 future organ, which at present scarcely reaches beyond the extremity of the rostrum, 

 and the outer branch is the scaphocerite in an undeveloped condition. 



Fig. 57. — Mandible, from 

 a drawing by v. Wil- 

 lemoes Suhm. 



