115 



suddenly a turn to the left as is shown more clearly on PI. XXIII, fio-. i6i. The buds of 

 siphons increase in size; they are more or less flattened dorso-ventrally, the ptera are well- 

 developed and do not bend one to the other, which would have altered the aspect of the 

 flattened siphon into a more rounded one. 



One of the young siphons (PI. XXIII, fig. i6i a) we detached and made a sketch of it 

 (PI. XXIII, fig. 162). It is the most distal one and shows already a different aspect from the 

 others; the ptera are first bent concave, later on convex; the central cavity of the siphon is 

 very clearly developed, and gets narrower and narrower near its apex, until it ends in a sharp 

 point; this also makes the young siphons of Dathyphysa Sibogae resemble more or less a 

 foliaceous bract of Physonccta. The length of this detached siphon is 6 mm. ; at its base there 

 is a very tiny protuberance of which we will speak later. Distally from the last siphon the 

 stem keeps the breadth of \ mm. along a distance of 10 mm. Then the stem diminishes in 

 breadth and varies from 3 — 2 mm. along its whole length. 



About 2,8 cm. from the above mentioned siphon we find three other siphons, situated at 

 a distance of 5 mm. one from the other. They are all bract-like, without pedicle, and with a 

 central canal ending in an acute point. The ptera have not curled up, therefore the siphons 

 have remained straight. The first siphon has a length of 10 mm., a breadth of 4 mm. of which 

 3 mm. belong to the transparent ptera; the second and the third have the same structure. 

 Behind this last third siphon the stem for a distance of 27 cm., shows no appendages; of 

 course the median groove or line is quite visible and as this line has not a straight course but 

 shows several turns, we understand that the stem has twisted itself continually. After these 

 27 cm., the first reproductive appendage is seen as a very small, tiny vesicle, at its side a 

 small hill-like enlargement of the stem. At intervals of 4 — 6 mm., we find successively the 2^^, 

 3^^, 4"\ 5^'\ b''' gonodendra which are already more developed, next a 7'^, and every time the 

 enlargement is also there. Near the 8"^ gonodendron, which this time bears a gonostyle, the 

 ,hill has changed into a small filament. The 9"^ gonodendron has been lost, but the filament is 

 yet represented and has attained a length of 2 mm., the io'>' gonodendron has increased in 

 size, the 11"' has disappeared and a filament of 3 mm. is to be seen. 



The next groups of appendages 12, 13, 14 consist of hill-like enlargements, but no 

 gonodendra nor filaments; the 15"^ shows a gonodendron of a length of 3 mm. with a distinct 

 gonostyle. Of the groups of appendages 16, 17, 18, 19, 20 (all of which are clearly to be 

 seen on the stem) only these peculiar filaments are left, in group 16 even attaining a length 

 of 18 mm. In these five last groups the length of the internodes varies from 5 — 9 mm. 



At last we found a group (21) where a siphon was left and we then found that these 

 filaments, which we could follow up to their very primary development as hill-like enlargement 

 near the smallest gonodendron, were stalks, pedicles of the siphons. In this 21^' group we also 

 see the gonostyle situated absolutely close to the base of the siphon stalk. The gonodendron 

 has disappeared. The pedicle of the siphon has a length of 18 mm., and is thread-like, it bears 

 a long siphon (30 mm.) of 3 mm. breadth in which the ptera are yet visible as very narrow 

 longitudinal stripes. The central cavity has very strongly marked circular muscles. 



Of considerable interest is the occurrence of a tentacle with tentilla at the base of the 



