212 



the Temnopleurinse), cannot be taken as definitely established, until all 

 the characters available, including the structure of the larvae, 

 have been studied and duly taken into consideration. The struc- 

 ture of the pedicellariae, of course, does not in itself give definite proof of 

 their affinities ; also these characters may, doubtless, have developed separ- 

 ately along different lines, as is seen from the case of Strongylocentrotus, not 

 to mention Glyptocidaris crenularis^). Therefore I would not consider e. g. 

 the position of the genus Loxechinus in the family Echinidse as defmitely 

 established, until it has been proved that its larva also belongs to the 

 Echinoid type. Still less can the position of forms like Notechinus magel- 

 lanicus and Pseudechinus albocinctus, where the characters of the pedicel- 

 larise are very indistinct, be regarded as settled, as long as we do not know 

 anything about their larvae. Upon the whole, the natural classification can- 

 not be found through arranging the forms diagrammatically after this or 

 that character; the interrelations and affinities being the result of organic 

 evolution and descent it is not likely that we will find the true expression 

 thereof by means of a diagram. 



As a definite result it may be stated that there is a definite larval 

 type charaicteristic of each of the three families, the Echinidae, 

 the Toxopneustidae and the Echinometridae. They may be shortly 

 characterized thus: 



The larvae of the Echinidae have in their first stage an elongated 

 body, supported by a long, more or less club-shaped body rod, the skeleton 

 forming no basket-structure. In the second stage there is no posterior 

 transverse rod, no posterolateral or vibratile lobes; epaulets are developed 

 at the base of the four main arms, often also one pair at the posterior end 

 of the body. Fenestrated rods are not known to occur within this type. 



The larvae of the Toxopneustidae have in their first stage a short 

 body, the body rod being short and, together with the recurrent rod, 

 forming a basket-structure (excepting the genus Lytechinus). In the second 

 stage there is a posterior transverse rod; posterolateral and vibratile lobes 

 are found, and there are often (always?) epaulets at the base of the four 

 main arms. The rods of the main arms simple or fenestrated. 



The larvae of the Echinometridae have in the first stage a short, 

 obhquely truncated body, supported by a compUcate basket-structure, the 

 recurrent rod being double. In the second stage there is a posterior trans- 

 verse rod; posterolateral and vibratile lobes are found, but no epaulets. 

 The rods of the main arms are fenestrated. 



1) Comp. the author's "Echinological Notes." II. A new principle of Classification Vid 

 Medd. Naturh. Foren. Kobenhavn. 1910. p. 31 note. 



