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as an established fact through the "Hnichiolnrin liibcmiai" of Gemmill, 

 affords another important aid for settling the question of I lie parentage of 

 the larva. Aslerias teiniispinn does not occur in the Atlantic to the North 

 of 40 Lat. X. Accordingly its larva could hardly he found off Ireland. 

 On the other hand Pedicelluslcr scxnidinlux is not known to occur farther 

 North than the Biscayau Gulf; but it is by no means improbable that it 

 does, however, occur in the deep-sea off Ireland. The result is then that 

 it seems highly probable that the " Slcll<isph;i j r<t niinihilis" is the larva of 

 Pedicellaster sexradiulux. 



The Ophiopluteus, in spile of the great number of "species" known, 

 appears to show only unimportant deviations from the original simple 

 type, which may perhaps be most nearly represented by the Ophioihrix- 

 larva. In the shape of the body there are only few features which may be 

 regarded as a higher specialization; such feature is the presence of vibratile 

 lobes at the base of the poslerolateral arms in the OpAwco/na-larva. The 

 presence of a ciliated tuft at the posterior end of the body, occurring in 

 various forms, may also be a specialized feature, probably acquired separ- 

 ately in various groups. Hut too little is known for forming a delinile judg- 

 ment of the value of this character. The ciliated ring in the posterior end of 

 the body of Ophiopluleux coroiutlux ("Echinodermen-Larven d. Plankton- 

 Exped." Taf. VI, Fig. (i), as yet quite a unique feature in Ophiurid-larvae, 

 may perhaps represent a furl her specialization of the apical tuft. Hut so 

 long as we do not know anything about the affinities of that larva ( its 

 skeletal structure is still unknown ) this question must remain unsettled. 



The length of the arms varies very considerably. The posterolateral arms 

 are generally much the longer and form the main floating apparatus of 

 Ihe larva; this is especially evident in the 0/j/j<o//in'.r-larva and Ophiopl. 

 opiilentus. where these arms are entirely unaltered during metamorphosis, 

 the young Ophiurid remaining attached to them and simply leaving them 

 by the lime it is giving up pelagic life. The arms of Ophinrid-larva- never 

 become actively movable swimming organs, no muscles connecting the 

 two parts of the body skeleton being present, contrary to what is often 

 Ihe case in Echinoid larva-. Generally the arms are very Ihin and narrow, 

 more rarely broad and Hal (as in Ophiopl. parado.nix and the Ophiocomu- 

 larva). The widening of Ihe arm poinls often found in preserved speci- 

 mens is probably only due to preservation. II is a curious fad Ihal Ihe 

 right anterolateral arm is often longer than the left one. 



A very conspicuous feature is the absence of poslerodorsal arms in Ihe 

 larva of Amphiura filiformis (Ojihiopluleus manciis). Also in Ophiopluteus 

 dubins (Echinodermen-Larven d. Plaiiklon-Exped. Taf. IV . Fig. 9 10) the 



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