Bd. VI: 8) TUE CRINOIDEA. 15 



The coalescence of the larva with the wall of the brooding- chamber observed in 

 two cases by K. A. Andersson is decidedly abnormal, and evidently has nothing with 

 a 'better nourishing« of the embryos to do, as Andersson is inclined to think. I have 

 not observed any such case of coalescence, though I have carefully studied the dif- 

 ferent stages of the larval development on an ample material. The larva; are sur- 

 rounded by the egg-membrane until they are ready to leave the marsupium. They 

 have the ciliated rings well developed and thus are not entirely lacking a free- 

 swimming stage, although, of course, this is very short, doubtless only so long as it 

 takes the larva to reach from the marsupium to the tip of the cirrus turned up be- 

 tween the arms, where it is going to attach itself ANDERSSON points out the ad- 

 vantage for the larva in thus giving up the free-swimming stage: they avoid the 

 danger of being transported into too deep water or other regions of the sea, where 

 they would sink down on a bottom unfit for them and thus perish. However, the 

 very short passage from the marsupium to the cirrus tip is connected with great 

 danger to the larvse — viz. of being eaten by their elder brothers and sisters! I have 

 found quite a large percentage of the Pentacrinoids to contain in their stomach the 

 half digested, but still perfectly recognizable, remnants of larvôe. Even quite young 

 Pentacrinoids, with the vestibulum just opened and the arms not yet developed, I have 

 found with an cmbr>'o almost as big as itself in its mouth. On account of the large 

 number of Pentacrinoids found attached in clusters to the tip of the upturned cirri — 

 Andersson has counted no less than 99 Pentacrinoids in one specimen — this danger 

 to the embryos is very real, and probably quite a large number of them must perish 

 in that way. This is, indeed, a very original way of feeding its offspring, but evidently 

 also very effective in stimulating the growth of those young ones, which have suc- 

 ceded in avoiding being eaten themselves on their short, but dangerous way from the 

 marsupium to the point of fixation on the tip of the cirrus. 



3. Thaumatometra nutrix n. sp. 



PI. V. 



Centrodorsal rounded-conical, low, only about half as long as wide. The dorsal 

 pole is rounded, a little rough. The ventral edge is straight, the interradial corners not 

 prominent. Cirrus sockets closeset, fairly distinctly arranged in columns (PL V, Fig. i). 



Cirri ca. XLV. Only a few of the upper, not yet fully developed, cirri are left; 

 judging from these the number of joints is ca. 20 (Fig. 14). No dorsal spines are 

 developed on these young cirri; but, judging from the cirri of the Pentacrinoids (PI. V, 

 F"ig. 6), there must be, at least, an opposing spine on the fully developed cirri. The 

 joints of the basal part are longer than broad, the distal joints much shorter; but, 

 again, it is uncertain, whether this is true also of the fully developed cirri. 



