20 



PENNATULIDA. 





all the more developed polyps, from the uppermost to the two lowest, large eggs (or larvae) are 

 seen; in the rhaehis, on the other hand, no sexual products are found. 



In the other specimens, about 150, that I have been able to examine, there is found, a so to 

 speak continuous series of stages, from the one just described down to a stage where the colony is 

 provided with only one pair of wings (I). Representatives of these stages may be found figured on 

 PI. II, figs. 17—24. 



One specimen (St. 24) of a total length of 29""", is provided with six distinct pairs of wings, and 

 below these with tiny rudiments of two pairs more. Each wing of the uppermost pair (I) consist of 

 three individuals: one fully developed polyp, one somewhat smaller, and one still a zooid; the next 

 wing (II) shows the same development. The wings III — V still consist of three individuals, but two 

 are in the zooid-stage, and the most ventral, youngest one, is already very small in IV, in V both are 

 very small; VI consists of only two individuals, a small polyp, and a small zooid; both the rudiments 

 (VII, VIII) consist of a larger and a quite small zooid. 



Another specimen (St. 24), of 25 mm , shows 5 pairs of wings and 2 pairs of rudiments; all the wings 

 consist of two individuals, the two uppermost of a developed polyp and one little developed, (wing I 

 on the right, however, has three individuals, being provided with a small zooid), the others of a polyp 

 and a zooid, both decreasing in size from above downwards; the rudiments consist of two zooids. 

 Other smaller specimens of 2i mm , also show 5 pairs of wings and 2 or 3 pairs of rudiments; others 

 again (25 — i6 mm ) 4 pairs of wings, 3 pairs of rudiments, others (17 — 13 1 "" 1 ) 3 pairs of wings, 3 pairs of 

 rudiments; others again 2 pairs of wings and 2 pairs of rudiments, PI. II, figs. 17, 18; in all these 

 specimens each wing consists of two individuals, a polyp and a zooid. Finally, we have several 

 specimens with only one pair of wings, and below one or two pairs of rudiments, and some specimens 

 with only one pairs of wings and no rudiments below (PI. II, tigs. 19, 20). Each wing in these latter, 

 however, consists also of two individuals, a developed polyp and a small zooid. 



The proportion between the rhaehis and the peduncle as to length is somewhat varying; some- 

 times the former, sometimes the latter is the longer, but often they are about equal in length. Devel- 

 oped sexual organs (sometimes larvae) are seen in most polyps, at all events in the developed ones; 

 in quite small (io mm long) specimens indeed with ouly one pair of wings and 2 pairs of rudiments, I 

 have seen large and developed sexual organs in one or both of the large polyps. Even the smallest 

 specimen, of 6 mm , represented in figs. 19, 20, shows (by clearing with glycerine) the sexual organs, though 

 not yet ripe. All the specimens have the two rows of zooids (z), but their number in each row is 

 very varying, increasing with the number of wings; in the specimens with only one pair of wings 

 only one or two zooids are found in each row. The small lateral zooid above each wing is only 

 seen in the tolerably well developed colonies. A common feature in all the specimens is further, that 

 the stem contains a calcareous axis, and that the rhaehis terminates above in a large zooid (Z). This 

 series of stages therefore is evidently a developmental series, in which the last-mentioned specimens 

 with only one pair of wings are the youngest. That this developmental series belongs to a species 

 of the genus Pennahtla is undoubtedly a fact; but the rather obvious supposition that the young 

 stages of the pale variety of Penn. phospltorea var. Candida before mentioned might be in question, is 

 inadmissible on account of the difference in the type of the spicules, and a closer comparison with 



