IO 
TH. MORTENSEN, 
(Schwed. Siidpolar-Exp. 
Also the pedicellariæ afford some differences. In the specimen from St. 17 they 
are invested by an unusually thick skin, but otherwise the structure of the valves 
is the same as in the normal specimens; in the specimen from St. 22, on the other 
hand, the valves differ rather considerably from those of the normal specimens, 
the opening being broadly triangular with the lower edge almost or wholly straight 
(PL XIII Fig. 9). 
On a closer examination I find that these spe- 
cimens show in their radioles a structure quite similar 
to that which I have described for Rhynchocidaris 
triplopora (Op. cit.). The curious tubes protruding 
through the thorns of the radioles are also found 
here, though not so strongly developed as in that 
species. In one case I have further found in a 
section of a radiole an organism* boring in the chalk 
matter, quite similar to that which I have described 
Fig. 3. Transverse section of radiole from f rom that species — in short, I think it can scarcely 
a specimen of Ctenocidaris speciosa in- 
fested with Echinophyces. s °i i. be doubted that these specimens are infested with 
Echinophyces , though I have, unfortunately, not 
found anything corresponding to the “spores” found in Rhynchocidaris. 
The differences from the normal specimens occurring in these two specimens 
I must then suppose to be due to the reaction against the parasite. It is further 
worth noticing that genital pores have apparently not yet been developed in these 
specimens, though they have appeared in the normal specimen of 18.5 mm. But on 
the other hand these specimens show the curious feature of having a small opening 
in the median interambulacral line at the ambitus (PI. XIII Fig. 1). In view of the 
fact that in Rhynchocidaris the genital openings have become transferred to the edge 
of the peristome in specimens infested with Echinophyces , it seemed not unreasonable 
to suggest that these curious openings in the middle of the interambulacra are the 
abnormally placed genital openings. In order to state this definitely I have opened 
one of the two specimens and found that this small interambulacral opening is really 
the genital opening. As was the case in Rhynchocidaris , the normal, genital duct 
exists but is, evidently, out of function. From the genital gland a new efferent 
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* In the same radiole I find here and there in the meshes made by the »hairs» on the ostracum a 
worm-like organism, irregularly rolled up — the same I found in the radioles of Rhynchocidaris. It looks 
very much like a Nematod. As I did not feel myself able to put beyond doubt whether it really is a 
Nematod or something else, I sent a preparation of it to my friend, the eminent specialist in Nematods, 
Dr. L. JÄGERSKJÜLD in Gothenburg, asking him to examine it. He kindly informed me that he thought it 
most likely a Nematod-Larva; but the material did not allow him to state anything more definitely about 
the animal. — There can thus scarcely be any doubt that the worm has nothing to do with the abnormal 
changes in these specimens; it only takes a place on the infested spines. 
