56 



PENNATULIDA. 



may be seen in the same colon}-, even in neighbouring' polyps; the ealyx-edge of the zooids is just as 

 indistinctly furnished with projections; most frequently, it seems to me, without such. The tentacles 

 are provided with a distinct streak of spicules; otherwise the retractile parts of the polyps are naked, 

 whilst the calyx is furnished with long spicules, placed densely and numerously on the abaxial 

 side. The size of the spicules agrees upon the whole fairly well with the measurements given bv 

 Kolliker. 



The arrangement of the polyps presents some variation, but the differences are evidently 

 connected with the different age and development of the colonies; also, the arrangement shown by 

 Kolliker for the type-specimens of 'the species Pr. thomsoni is represented here. A common feature 

 in all the specimens is, that along the dorsal median line of the pen runs a distinct, sometimes rather 

 broad streak devoid of polyps and zooids [n, figs. 4, 5, 6); it is broadest in the lower part of the pen 

 towards the peduncle; this streak is uncoloured (or yellowish white) like the peduncle. A similar 

 streak, more or less distinct, also runs along the opposite, ventral surface («' figs. 6, 7, 8); it begins 

 below at the peduncle where it is almost as broad as the dorsal one, but it very soon becomes 

 quite narrow, often only seen as a very fine line, in some specimens even interrupted in several 

 places by polyps placed quite mediauly. Otherwise the whole rhachis is covered with polyps and 

 zooids; the latter occur in very large numbers and fill all the interspaces between the polyps. On 

 the lowermost part of the pen (figs. 6, 8) undeveloped polyps together with zooids form a long, wedge- 

 shaped streak on either side, between the two naked streaks mentioned above. 



In the most developed specimens the polyps may be said to be arranged in three or four 

 longitudinal rows on either side; but if we follow Kolliker, and take into consideration the oblique 

 rows ascending towards the dorsal surface, each of these contains generally four, five (or in a single place 

 six) polyps (comp. fig. 7); in reality, the arrangement on either side is nearest quincuncial. Less 

 developed specimens show two longitudinal rows on either side with two or three polyps in each 

 oblique rows; the least developed show something between one and two rows, i. e. they approach the 

 arrangement that may be found in P. carpenteri; in these specimens there seem to be transverse groups of 

 three polyps: one belongs to the right side, one to the left whilst the middle one is apparently placed 

 in the ventral median line ( Pr. lofotense ■). In places where the ventral median line is only indicated (it 

 may be very difficult or in some places quite impossible to see it) the real condition is that a polyp 

 has been added alternately on the right and the left side inside the one belonging to the original 

 first row (the dorsal polyps) nearer to, or, as it were, in the ventral median line; oblique rows 

 cannot be said to be marked here as in the others; or, if they are present, they must be growing 

 in the opposite direction and alternating in such a way, that opposite to an oblique row of two 

 polyps on one side there is a solitary polyp on the other side. In the table below, of all the speci- 

 mens which have hiherto been described and which I think must be referred to the same species, 

 some of these features have been indicated and some measurements given. The statement of the 

 total length means here only the length of the specimen in question, as no specimen is complete. 

 This species probably grows to as greath a length as such forms as Halipteris, Pavonaria or 

 Funiculina. 



