53' 
rig. 13. Apical 
system of 
Macropneustes 
Pellati Cott. 
(From Lovén). 
natural thing would be to regard it as representing the genital 
2 alone, homologous to the madreporic plate of the ethmophract 
Amphisternata, and of the Echinoids in general, only grown exces- 
sively (Fig. 13). That this is the correct view, 
is shown by the development of the plates of the 
apical and anal system. This development has 
been studied by Lovén, A. Agassiz and the 
present author, especially in Abatus cavernosus 
(and cordcitus). In my work „The Echinoidea of 
the Swedish Southpolar Expedition 41 *) (p. 75—78) 
the development of the apical system of Abatus 
cavernosus is treated at some length. It is shown 
that there is no central or suranal plate developed 
(cf. PI. XVII, fig. 9); on the other hånd a distinet genital 5 is 
developed at the hind edge of the anal area. (Fig. 14). It is thus 
made certain that Loven’s view 
of the madreporite representing 
the genital 2 -J- the central plate 
-J- the genital 5 cannot be main- 
tamed. Also in Amphipneustes 
Koehleri Mrtsn. the same holds 
good, as shown by the young 
stage figured in PI. XVIII, fig. 2 
of the work quoted. In the 
light of the facts thus made 
known regarding the development 
Fig 14. Apical system and sur- 0 p the apical system in Abatus 
roundings oi a young Abatus caver¬ 
nosus. The plates numbered 1, 2 .. .5 cavernosus, the young stages of 
are the genitals, those numbered I, Echmocardium flavescens , Bris- 
II—V the oculars. (From. Th. . 
Mortensen) aster fragihs , Hemiaster exper- 
gitus figured by L o v é n (On 
Pourtalesia. PI. XV. Fig. 173) and by the present author („Ingolf 44 - 
Echinoidea. II, p. 98, fig. 17. PI. XIII. Fig. 2), though already 
9 Schwedische Siidpolar-Expedition. Bd. VI. 4. 1910. 
