Bd. VI: 4) 



THE ECHINOIDEA. 



39 



bryonal spines in the smallest specimen in hand, 1.4 mm. in diameter. The primary 

 spines of the young specimens (PL XVI. Fig. 12) are thorny and end in a distinct 

 central thorn; this is also to be found in the grown specimens, if only the spines 

 are unbroken, which is, however, comparatively seldom the case, they being very 

 fragile. Spines with the outer part regenerated are very commonly seen; also in such 

 spines the central thorn may be distinct. The secondary spines of the young speci- 

 mens are also thorny and have a small central thorn in the point (PI. XVI. Fig. 11). 



The spicules (PL XVI. Fig. 9. a) are not very numerous; they are very slender, 

 bihamate. Also such spicules occur, which are not bent at the ends (PL XVI. 

 Fig. 9. b); they are probably developmental stages of the usual form. No spicules 

 are found in the walls of the intestine, axial organ or genital organs; the latter are 

 not coalesced. 



Concerning the pedicellaria; I must refer to the description given in the »Ingolfv 

 Echinoidea and by DODERLEIN (Op. cit). The interesting observation was made by 

 DODERLEIN that this species has two kinds of globiferous pedicellariae, a larger and 

 a smaller one, the latter generally with only one lateral tooth. I have found this 

 small form * to occur constantly, though in varying numbers; sometimes it is rather 

 plentiful, sometimes very scarce, especially among the specimens from Stations 2 

 and 44 it even appears to be totally wanting in a few of the specimens. It is 

 mainly found on the abactinal side. It is an interesting fact that both forms of 

 globiferous pedicellariae have double poison glands, while in Sterechinus the glands 

 are single, with a median depression towards the point. In the small form it ap- 

 pears that the two glands are always of different size (PL XVI. Figs. 3, 19, to 

 compare with PL XVI Fig. 15, representing a globiferous pedicellaria of Sterechinus 

 Agassizii). — It is to be remarked that quite young specimens have only the small 

 form of globiferous pedicellaria;, typically developed; the larger form appears at a 

 size of ca. 5 mm. — A curious case of abnormality was observed in this species, 

 viz. a triphyllous pedicellaria with two heads (PL XVI. Fig. 10). 



The sphaeridiae form a not very close series, reaching to the 10th — nth ambu- 

 lacral plate; in the larger specimens I count ca. 20 in a series. They are oval, smooth. 



This species was taken by the Swedish South Polar Expedition on the follow- 

 ing stations: 



* In one of my preparations I find some small globiferous pedicellaria; with the valves quite differently 

 shaped,, being very much like those of Protocentrotus annulatns (as figured in the Echinoidea of the Ger- 

 man Southpolar Exped. PI. XVI Fig. 5) with the blade quite open and with one tooth on either side. 

 Having observed this, I carefully reexamined the specimens but was unable to find more than the usual 

 small form. Accordingly I do not venture to state that these pedicellaria: really occur in magellanicus ; on 

 the other hand I do not see, how they could have come there, if they do not belong to this species. — 

 They are distinctly different from those of Loxech. alius, the only species with globiferous pedicellariae of 

 the Pareckinus-type found along with magellanicus. — The question cannot be decided, but I have thought 

 it right to mention the matter. 



