REPORT ON THE SCHIZOPODA. 159 



i 



The Antennulce (figs. 1-5). — These limbs, constituting in the Xuuplius and Meta- 

 nauplius stages simple, nou-articuhxte stems, exhibit each of them (fig. 1) in the earliest 

 Calyptopis stage described above, and apparently corresponding to the second Calyptopis 

 stage of Nyctiphanes, a slender non-articulate peduncle, 'bearing at the apex two very 

 small, uniarticulate flagella, the outer a little longer than the inner, and provided with a 

 pair of slender bristles and two sensory appendages. 



In the following (last) Calyptopis stage, these limljs (fig. 2) are much moi-e fully 

 developed, the peduncle being rather strong, and di\dded into three distinctly defined 

 joints, of which the basal is b)' far the largest, and 2)rojects at the end exteriorly as a 

 strong spine, denticulate at the inner edge, and reaching almost to the end of the 

 peduncle. The second joint is quite short, and bears at the inner edge two strong 

 ciliate setse. The last joint is almost twice as long, and has a single bristle internally. 

 The flagella do not exhibit any essential difference from those in the preceding stage. 



In the Furcilia stages the number of bristles along the inner edge of the peduncle 

 has become somewhat augmented, and the two flagella have slightly increased in length, 

 though still uniarticulate. In the last of these stages (see fig. 3) the long apical bristles 

 of the flagella are lost, and the two sensory appendages of the flagellum, arising originally 

 from the tip, are now aflixed to a ledge-like projection of the inner edge, near the base. 



In the Cyrtopia stages the peduncle (fig. 4) has a somewhat greater similarity to 

 that of the adult animal, the spine springing from the basal joint being somewhat 

 reduced in size, and both the flagella considerably elongated and divided into a number 

 of distinctly defined articulations. 



But not tin the last stage described above — the first post-larval stage — do the 

 antennulse (fig. 5) assume their definitive form, differing only from those of the adult 

 animal in the dorsal leaflet of the basal joint being still but slightly indicated, and in 

 the flagella having not yet attained their full length. 



The Antennce (figs. 6-8). — The structure of these limbs is much the same throughout 

 all the Calyptopis and Furcilia stages. They diff"er widely from those in the adult 

 animal both in form and function, constituting, as they do, very mobile, biramous natatory 

 organs of much the same appearance as that described above in the larvae of Nyctiphanes, 

 and strongly reminding one of the second pair of antennae in the Calanoid Copepoda. 



In the last Furcilia stage some of the natatory setae are sometimes, however, found 

 to be obliterated (see fig. 6), though in other respects no difference in the structure of 

 the organs has yet arisen. 



But in the next, or first Cyrtopia stage, these organs (fig. 7) arc seen to have 

 suddenly undergone a total alteration alike in structure and function, having lost their 

 great mobility, and assumed a form more in accordance with that of the adult animal. 

 The basal j)art is shortened and has lost its segmentation, whereas a slender spine has 

 sprung from the end externally, representing the basal spine of the adult animal. Of 



