Febeuary 14, 1896.] 



SGIENGE. 



245 



him that it is necessary to abandon tlie hypo- 

 thesis above mentioned, at least until some 

 other function is proved for the terminal disk. 

 Pelseneer seems to think that the rostral papilla 

 may be covered with an external shell in the 

 living animal, but for this there is no evidence 

 as yet, and hardly any justification. 



In most specimens the peripheral cortex has 

 two lobes covering the lateral planes of the 

 shell and leaving a certain portion of the outside 

 of the whorl, dorsal and ventral, in front of the 

 terminal disk, more or less exposed. Owen 

 describes the epithelium as extending out over 

 these areas of shell but not entirely enclosing 

 them. Steenstrup describes a specimen in 

 which the shell "was distinctly covered dor- 

 sally and ventrally, where the skin grew thin 

 above it." Upon this Pelseneer observes, "As 

 one might expect, this last assertion is abso- 

 lutely incorrect, ' ' and ' ' there is no portion of 

 the integument, however thin this may be, 

 which passes over the shell, contrary to the 

 opinion of Owen and Steenstrup. ' ' 



How difiicult is the r61e of infallibility, may 

 be judged by the fact that, in the National 

 Museum specimen of Spirula, not only do the 

 epithelial and ohromatophoric layers extend, 

 where untorn, completely over the dorsal ex- 

 posure of the shell, but the underlying outer 

 muscular coat,* as thick and tough as parchment, 

 does the same; while, on the ventral side, the 

 rags of this covering torn by the fish's teeth 

 show that here also the shell was completely 

 covered. The solid basal coriaceous part of the 

 integument preserves its usual form. Huxley's 

 figures of Spirula Peronii (PI. I., figs. 1-3, 5-6) 

 indicate the same state of affairs with great 

 clearness, and the ragged edges of the torn in- 

 tegument are perfectly depicted. These are, 

 however, interpreted by Pelseneer thus: " The 

 margins of the openings appear to be fixed, and 

 to have thus sent short irregularly cut pro- 

 longations over the shell." It would be rash, 

 not having seen the specimen, to assert that 

 these ' prolongations ' are simply the rags of 

 the former covering, but it is certain that in 

 one species of Spirula (that referred to as 8. 

 australis by Pelseneer) in the adult animal the 



* Corresponding to Pelseneer's first and second 

 layers. 



shell is completely covered by the integument, 

 as was the opinion of Steenstrup. 



Adams and Reeve have figured a very young 

 Spirula, which Owen believed to be complete, 

 in which the terminal disk was absent and the 

 lateral lobes cover only a small part of the last 

 whorl of the shell. Pelseneer has figured hypo- 

 thetical stages of development for Spirula show- 

 ing a gradual enlargement of the lateral lobes 

 of integument. In most specimens so far ob- 

 served, portions of the shell are certainly un- 

 covered. It is not an extreme hypothesis to 

 suppose that in the fully adult animal the in- 

 tegument in most cases will wholly enclose the 

 shell. 



The shell of Spirula is enrolled with the ven- 

 tral side concave, and Pelseneer observes that 

 the ' ' other molluscs with rolled up univalve 

 shells present, when they have not under- 

 gone torsion, a dorsal or exogastric rolling up, 

 e. g. , Nautilus, embryonic Patella and Fissurella. ' ' 



The learned doctor forgets that Patella and 

 Fissurella are rolled up in opposite directions, 

 and that Fissurella, if prolonged into a tube and 

 coiled as it begins, would have an ' endogastric ' 

 whorl like Spirula. Aliquando dormitat Homer us. 



In 1878 I saw in the Godefroi Museum, since 

 acquired by the city of Hamburg, a large series 

 of Spirula from the South Seas. They were 

 partly fragmentary, but I believe comprised 

 several perfect specimens which might throw 

 light on doubtful points. The specimen in the 

 National Museum came from a fish trawled in 

 324 fathoms in the northern part of the Gulf of 

 Mexico, between the delta of the Mississippi 

 and Cedar Keys, Florida. The color is yellow- 

 ish white, with ferruginous and dark purple 

 dotting profusely distributed. The specimen is 

 a female. The temperature of the water at the 

 bottom was 46°. 5 F. It had evidently just been 

 seized by the fish, for, except the lacerated epi- 

 dermis, it is in most perfect preservation. 



In conclusion we may note that perhaps the 

 most important result of Dr. Pelseneer's analysis 

 of the characters of Spirula is its final reference 

 to the Oigopsid group. Owen had stated facts 

 also confirmed by the data of paleontology 

 which should have resulted in this classification 

 more than fifteen years ago; but there has been 

 a singular delay in accepting it. After the full 



