REPORT ON THE CRUSTACEA MACRURA. 



459 



'2 - G7 mm. to 279 mm.; that is, rather more than one-tenth of a millimetre. All parts 

 appear to have slightly increased in size except the rostrum, which is a little shorter, 

 and the carapace, the width of which has slightly decreased. They may be the young of 

 distinct species, but since both were taken in the Pacific Ocean, they are probably 

 successive stages of the same species. 



The great point of interest is the presence of features of the permanent character in 

 the older specimen. The long neck or cervix is for the first time made apparent by means 

 of a deep depression on each side, between the 

 cephalic organs and the oral appendages, and a 

 strong tooth on each side of the oral organs is 

 here distinctly prominent and apparently, from 

 Willemoes Suhm's drawing, relatively more 

 important than in the adult. 



The rostrum is still a prominent feature, 

 and projects forwards nearly to the extremity 

 of the first joint of the peduncle of the first 

 pair of antennas. The tooth on the outer frontal 

 angle is more prominent. 



The ophthalmopoda have increased in length, 

 but are not much altered in form, and the ocellus is 

 still visible in the centre above the cerebral mass. 



The first pair of antennas is figured as consisting of three joints, of which the first is 

 long, as in the preceding specimen, the second about one-third the length of the first, and 

 the third longer than the second and terminating acutely as if it were the future 

 flagellum. This probably is divided in the specimen by an articulation that is not 

 immediately distinguishable at the base of the first joint ; the future acoustic organ is 

 visible in an incipient condition. 



The second pair of antenna? has increased considerably in length, and the scaphocerite 

 has assumed more of the features of the permanent character ; the cilia which fringed the 

 inner margin are, however, but few, and very minute and distant. 



The carapace has increased but little in length proportionately, but that growth 

 which has taken place is anterior to the oral appendages, thus carrying the antennas 

 and ophthalmopoda forwards, and commencing the development of that long, neck-like 

 form, which is so peculiar a feature in this genus. 



The oral organs do not appear to have undergone any great change, and the pereio- 

 poda, which are still four pairs, correspond closely with those of the preceding, all 

 having somewhat increased in length, except the posterior pair, which is relatively 

 smaller .than that of the preceding. 



The pleon and its appendages appear to be in the same relative proportion of 



Fig. 62.— "Telson (z)with Fig. 63.— v, "Last somite 

 sixth pleopod (v) ; seen of the pleon with telsou 

 from above." attached." 



