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DE. E. VON WILLEMOES-SUHM ON THE 
part of the pupa is the large shell-gland (fig. 24, gl 2 ), the function of which is to supply 
first the materials for the five primitive valves of the shell, and then the shells them- 
selves, which, according to Claus’s and my own observations, are formed after those 
small valves and separately from them, so that the former always remain in the shell 
and are easily recognized by their peculiar cellular structure. 
Traces of an ovary have also been found in the pupa stage, and figured as seen under 
a low power in fig. 28. 
IV. The metamorphosis of the Cypris into the Lepas. 
The pupse swarm round the dead Velellce , and settle by means of their hooks and 
suckers as soon as they find a suitable place. None of the metamorphoses, therefore, 
are easier to study than these, as one young colony caught during the season of their 
development shows all the stages — the pupa which has just settled and not yet changed 
its form (Plate 15. fig. 24), the same after its head had grown out and when its 
Cyj?m-shell and natatory feet are just going to be cast off (fig. 25), and the perfect 
young Lepas (fig. 26). Still what happens within is more difficult to observe, as the 
transparency, which hitherto guided us in our researches, is less and less to be found as 
the pupa develops. 
The growing out of the head and the appearance of the feet in that part of the 
abdomen which in the Cypris (fig. 24, la) is divided by ridges and chitinous lamellae, 
is the first thing that happens; and now one may also see very faint traces of the 
cellular tissue of the primitive valves. The eyes, however, are still in their position, 
and the Cypris- shell still covers the body. The next stage (fig. 25) is the loosening 
of the Cypris- shell and of the moulted natatory feet, which in fig. 25 may be seen just 
coming off. Underneath six pairs of cirri ( p ) may be seen, which still differ from those 
of the adult Lepas in being less segmented and not so hairy. The three primordial 
valves are now fully formed, and are very striking from their regular network of 
cellular tissue. The eyes of the Cypris stage have already lost their proper position, 
but may still be seen as black pigment-spots, which are about to be absorbed ; they 
look like pictures which have lost their frames, and will soon entirely disappear. The 
upper lip is now very prominent, and the organs of digestion are shining through the 
valves in formation. 
From the two large glands underneath the mouth, in front of the stomach, ducts 
filled with granular secretion may be seen going down to the antennse (fig. 25, a ), 
which by-and-by have to form a gelatinous ball which finally absorbs the fragment of 
Velella. 
In this stage the upper portion is 1 millim. long, the grown-out head having a length 
of 0-7 millim. It now throws off entirely all the larval remains; the valves of the 
Cypris-sYieW drop with the old feet and caudal appendages, and round the primordial 
valves, which indicated already the position of the larger ones, a more solid skeleton 
