522 TRANSACTIONS OF SECTION D. 
keeping the female from attaching herself to any firm support. It would appear 
that the introduction of the arms of the male into the mantle-cavity interferes 
with the respiration of the female, and that she makes desperate efforts to escape 
as soon as she can attach herself to any neighbouring object. In this respect 
there is a marked contrast between the behaviour of these two genera, and it is 
greatly to be desired that observations should be made on other forms, but the 
difficulties in the way of this have hitherto proved insuperable. 
Although, as we have seen, but little is known of the actual working of the 
hectocotylised arm, there are differences in the structures set apart in the female 
for the reception of the spermatophores, which correspond with the different 
arrangements of the hectocotylus in the male. For example, in Polypus (Octopus) 
the spermatophores are deposited in the termination of the oviduct; in Rossta 
there is a large plicated area surrounding the mouth of the oviduct for their 
reception; whilst in the nearly related Sepiola there is a pouch-like depression of 
the integument lying beside the mouth of the oviduct for the same purpose (von 
Maehrenthal) (29). In Sepia, Loligo, and the other Myopsids in which the 
ventral arms are hectocotylised the spermatophores are received upon a specially 
modified area lying just to the ventral side of the mouth. 
From this all too brief sketch of the function of these organs we may now 
return to the question of the systematic value of the modified arm of the male. » 
Professor Steenstrup was firmly convinced of the paramount importance of the 
hectocotylisation as a classificatory character, and he seemed to cling to this 
belief almost with the ardour of a devotee for a religious principle. In 1881 he 
published a memoir (40) in which a new classification of the genera Sepia, 
Loligo, Rossia, and some other forms was propounded, based avowedly on the 
position of the hectocotylised arm; and when this scheme was attacked by the late 
Dr. Brock of Géttingen (8) he defended it vigorously in a further communica- 
tion (41), placing at its bead the following thesis, much in the same spirit as 
Luther nailed his famous theses to the church door at Wittenberg: ‘ Hecto- 
cotylatio bene observata et rite considerata divisionibus naturae semper congruit ; 
incongrua divisionibus, eas arbitrarias et factitias esse indicat.’ 
Steenstrup further explains that the point of most consequence is which pair 
of arms is affected by the hectocotylisation, whether the first, third, or fourth 
pair; next in importance comes the nature of the modification; while the question 
whether the right or left arm is affected is quite insignificant. It will be our 
business to consider how far the Danish naturalist’s position is justified in the 
light of our present knowledge. 
It will first be necessary to set out the facts of the case as ascertained up to 
the present date, and, as no complete statement is accessible, it will be con- 
venient to give a list of the genera of recent dibranchiate Cephalopods, showing 
which arm (or arms) is affected by the modification under discussion. 
TaB_e I. 
List of Genera of Recent Dibranchiate Cephalopoda showing the position 
of the hectocotylised arm or arms, with an indication of the modifica- 
tion found. 
1, 2, 3, 4=the position of the arm or arms, reckoning from the dorsal to the 
ventral. 
R. and L. =right and left. 
0=no hectocotylised arm is present. 
?=no information is at present available. 
OCTOPODA. 
Cirroteuthide. 
Cirroteuthis 0 
Stauroteuthis 0 
Froekenia . . 2 
Opisthoteuthis . 0 
