526 TRANSACTIONS OF SECTION D. 
He thus made two main divisions according to whether hectocotylisation 
affected the first or fourth pair of arms, and placed the four genera Sepiadariwm, 
Sepioloidea, and Idiosepius (notwithstanding their Sepiola-like form) with Spirula, 
apart from Sepiola and Rossia,and along with Sepia and Loligo. It becomes 
necessary now to inquire how far this classification is justitied by what we know 
of the morphology of the forms concerned. 
It will be convenient to deal in the first place with Spirula, which has always 
been of great interest on account of the unique structure and position of its shell. 
It still belongs to the greatest of zoological varieties, only a dozen specimens with 
the soft parts having been obtained, of which one alone proved to be a male. This 
was examined by Sir Richard Owen (34), who described the hectocotylisation as 
affecting both the ventral arms, which are much enlarged, exceeding the others 
both in length and thickness: they are quadrangular in section, devoid of suckers, 
and the right is much larger than the left. The other arms appear to have a 
round truncated extremity which may be a secondary modification. The relation- 
ships of Spirula have recently been made the subject of inquiry by Professor Paul 
Pelseneer, who completed the memoir in the ‘Challenger’ reports begun by Pro- 
fessor Huxley (17), and by Dr. Einar Loénnberg (30) of Stockholm, who dissected a 
specimen obtained for him from Madeira by the late Captain Eckman. These two 
investigators arrived at different conclusions regarding its systematic position. 
Pelseneer regards it as an Cigopsid on the strength of the following charac- 
ters :— 
1. The open eyelids admitting the sea-water to bathe the cornea. 
2. The elongated central nervous system. 
3. The short junction of the visceral nerves behind the anus. (It may be noted 
that Myopsids vary in this respect.) 
4, The well-developed anterior salivary glands. (Hereit must be remembered 
that these glands are present in Rossta and not in Sepiola.) 
5. The liver is not traversed by the cesophagus. (Here, again, the Myopsids 
vary. 
fy The posterior aorta has a recurrent branch. 
7. The renal aperture is sessile, not mounted on apapilla. (Yet several Gigopsid 
genera, e.g., Thysanoteuthis, Histioteuthis, Chiroteuthis, and Mastigoteuthis, have 
renal papillee.) 
8. The tentacular arms are incompletely retractile. 
The following may be mentioned as Myopsid characters in Spirula:— 
1. The single oviduct on the left side. 
2. The arrangement of the lamellee in the nidamental gland resembles that in 
Sepia and Loligo. 
3. All Gigopsids (except Gonatus) have the suckers in two rows, whereas 
Spirula has more. 
4, Both ventral arms are devoid of suckers, which in Idiosepius are much 
reduced innumber. (Steenstrup says to one.) 
5. The body is elongated and cylindrical, as in Idiosepius. 
6. The fins are rudimentary, and terminal also, as in Idiosepius. 
7. The terminal pit in Spirwa is compared with a similarly situated depression 
in Idiosepius. 
The last three characters are adduced by Steenstrup to justify his inclusion of 
Spirula and Idiosepius in the same family, but they can hardly be regarded as of 
great importance. The form of the body and position of the fins are easily modified 
in response to environment ; the depression in the posterior extremity of Idtosepius 
does not. seem.to be constant, whilst, as regards the resemblance of the hecto- 
cotylised arms, itis, in my opinion, more apparent than real. In Spzrula the ventral 
arms are much enlarged, quadrangular, and suckerless; in Idosepius they are 
