REPORT ON SPIRULA. 
31 
however, the opinion that Spirula is a Myopsid, 1 and this view is generally adopted in 
the treatises on Conchology. 
The facts presented above relative to the organisation of the genus show that it has 
nothing at all to do with the Myopsids, but that, according to the following characters, it 
is certainly an (Egopsid : —Eye with cornea (false cornea) widely open ; central nervous 
system very elongated ; short junction of the two visceral nerves to the back of the 
anus; “anterior” salivary glands well developed; liver not traversed by oesophagus, 
aorta, &c.; posterior aorta with recurrent branch (genital); renal orifices sessile ; tenta¬ 
cular arms incompletely retractile. This conclusion that Spirula (whose archaic 
character is incontestable 2 ) is an (Egopsid agrees with the fact that the (Egopsids are 
certainly the most archaic of the Dibranchiates. 
If we wish now to seek for the origin of Spirula we must evidently acknowledge 
that it separated very early from the stock of the (Egopsids, before the acquisition of the 
rostrum characteristic of all the testaceous Dibranchiates, and before the phragmocone 
(corresponding to the shell of the Molluscs) had become internal and had been reduced 
(it is already more so in the Belemnites than in Spirula). This conclusion agrees with 
the fact that Spirula, in the direction it has followed, has undergone some specialisa¬ 
tions, which are not observed in the generality of (Egopsids, for instance the loss of the 
right oviduct (of which there have not been found any distinct traces) ; and the 
acquisition of accessory nidamental glands. 
In short, we may say that Spirula must have come from a Belemnite-like form, still 
without rostrum (as Belemnoteuthis), the right phragmocone of which, still external 
(at least in part), is rolled up in an inverse sense to that of Nautilus . 3 
1 Steenstrup, op. cit., p. 237 : “ Non seulement parmi les Myopsides, mais aussi dans la division des 
Sepiens.” 
2 Especially on account of the following characters : shell still partially external ; anus without valvules, 
as in Nautilus ; kidneys still without communication with each other. 
3 It appears most probable that Spirula comes from a straight ancestor and not from a rolled form in the 
inverse sense (as Nautilus ), for there is nothing in its organisation which shows that it has been unrolled 
and then re-rolled in the inverse sense. 
