452 



NA TURE 



[August 29, 1907 



THE BRITISH ASSOCIATION. 

 SECTION n. 



OrExiNG Address bv William E. Hovle, M.A., D.Sc, 



President of the Section. 



(/Ibn'd^ed.) 



The impression left upon my mind by a score of Presi- 

 dential Addresses to this Section, wliich it has been my 

 privilege to hear, is that the speaker who treats of the 

 subject matter of his own researches has the best prospect 

 of making his remarks interesting and profitable to his 

 audience. It is, therefore, in no spirit of egotism that I 

 invite your attention this morning to the small and 

 economically unimportant group of the Cephalopoda. 



Some of my predecessors have been men who walked, 

 so to speak, on the heights ; who undertook the culture, or 

 at all events the surveillance, of large domains. The 

 extensive views and broad principles which they have thus 

 been able to lay before the Section have been such as at 

 once to compel the attention of all who are interested in 

 any department of biology, or indeed of any branch of 

 science at all. Mv own case has been far different ; the 

 plot I have tried to cultivate has been a very small one, and 

 I have had but little leisure to peep over the fence and 

 see what my neighbours were doing. 1 come before you, 

 therefore, as a specialist, and not only so, but as that 

 most humble kind of specialist — a systematist (a " mere 

 systematist "is, I believe, the common phrase) — one whose 

 main work has been the discrimination and definition of 

 genera and species. I feel that some apology is necessary 

 in asking zoologists of all departments to step for an hour 

 into my particular allotment and see what has been going 

 on there during the last few- decades. 



Before inviting you to enter, however, I should like to 

 plead that even the systeinatist has his uses ; for, properly 

 considered, what is the systematic arrangement of any 

 group of animals but the condensed formal expression of 

 our present knowledge regarding its morphology, ontogeny, 

 and phylogeny? Furthermore, how could the varied and 

 complex probiems of geographical distribution be attacked 

 without the materials prepared by the systematist ? 



Having said this much by way of apology and defence, 

 let me invite you w'lthout further prelude to consider two 

 or three questions suggested by the study of the Cephalo- 

 poda. 



Just half a century ago (.\ugust i, 1857), there appeared 

 in the Anna\s and Magazine of Natural History the trans- 

 lation of a paper by the late Prof. Steenstrup, of Copen- 

 hagen, which has ever since been regarded as marking 

 an epoch in our knowledge of the Cephalopoda. The con- 

 sideration of the scope and significance of this memoir may 

 profitably, engage our attention for a short time. In re- 

 searches which were then comparatively recent, Virany 

 and Vogt and Heinrich Miiller had shown that, in the 

 genera Trcmoctofus and Argoimuta, the heclocoiylus, a 

 supposed parasitic worm which had been found in the 

 mantle-cavity of the female, was in reality one of the arms 

 of the male which had become detached and found its 

 way thither, bearing with it the fertilising element — a 

 procedure quite unique, not only among the Cephalopoda, 

 but also among the MoUusca, if not in the whole animal 

 kingdom. The gist of Sleenstrup's discovery was that, 

 although the separation of an arm was peculiar to very few 

 forms, the modification of one or other of the arms for 

 reproductive purposes was of common occurrence among 

 the Cephalopoda ; and, furthermore, that the situation of 

 the particular arm, which was so modified, varied with 

 the systematic position of the genus in question, and was 

 constant through the main divisions of the class. To this 

 less extensive modification of the arm he gave the name 

 " hectocotylisation." 



Stimulated by this discovery, other zoologists examined 

 the Ceplialopoda in their possession, and described the 

 modifications in various genera, and now it is universally 

 recognised that no definition of the Cephalopod is complete 

 which does not include a description of the position and 

 form of the hcctocotylised arm. The descriptive anatomy 



NO. 1974. VOL. 76] 



of this organ is fairly well known. Out of twenty-two 

 families, which may be regarded as well established, its 

 structure is known in a number of genera in no fewer than 

 twelve, whilst of the remaining ten it has been more or 

 less conclusively shown that in seven no modification of the 

 arm takes place, so that there are only three families in 

 which we are still without any information regarding it. 



Our knowledge of the physiology of the apparatus has 

 not, however, advanced with anything like the same 

 rapidity. Even in the case of those forms where a true 

 hectocolylus is found {Argonaiila, Trcmoctopus, and 

 Ocythoe) it is not known for certain whether the fertilising 

 arm is deposited by the male in the mantle-cavity of the 

 female (as I think is most probable), or whether (as is 

 stated by some writers) the arm breaks off when mature 

 and finds its own way to its destination. This much is 

 certain, that for some time after its detachment it pos- 

 sesses the power of independent movement. 



As regards the function of the modified but not detach- 

 able arm, we h;ive the important and interesting observ- 

 ations of Racovitza made at Roscoff and Banyuls on 

 the genera PolyjtKs (Octopus) and Sepiola. It appears that 

 in the first of these forms the extremity of the hectocoiylised 

 arm of the male Is introduced into the mantle-cavity of the 

 female, both individuals resting on the sea-bottom and 

 at some distance from each other (about 25 cm. in 

 the case of a male measuring i"25 m. in total length), 

 .Although after an encounter the female appeared to flee 

 the embraces of the male, and although the males, when 

 two were placed in the same tank, fought with each other, 

 there was no sign of any combat between the sexes as 

 was described by Kollmann. In Sepiola the female i« 

 roughly seized by the male, and hi Id with the ventral 

 surface uppermost ; the two dorsal arms are introduced 

 into the mantle-cavity, whilst the oiher three pairs hold 

 the female firmly. 1 he efforts of the male are directed to 

 keeping the female from attaching hersrlf ic any firm sup- 

 port. 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 inarked 

 contrast between the behaviour of these two genera, and 

 it is greativ 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 hectocoiylised arm, there are difler- 

 enees in the structures set apart in the female for the 

 reception of the spermatophores, which correspond with 

 the different arrangements of the hectocolylus in the male. 

 For example, in r'olypus (Octopus) the spermatophores are 

 deposited in the termination of the oviduct ; in Rossia 

 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). In Sepia, Loligo, and the other 

 .Myopsids in which (he ventral arms are hectocoiylised the 

 spermatophores are received upon a specially modified area 

 lying just to the ventral ?ide of the mouth. 



From this all loo 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. Prof. Steenstrup 

 was firmly convinced of the paramount importance of the 

 heclocotylisalion as a classificatory character, and he 

 seemed to cling to this belief almost with the .ardour of 

 a devotee for a religious principle. In iSSi he published 

 a memoir in which a new classification of the genera 

 Sepia, Loiigo, Rossia, and some other forms was pro- 

 pounded, based avowedly on the position of the hecto- 

 coiylised arm : and when this scheme was attacked by the 

 late Dr. Brock of Gbttingen, he defended it vigorously 

 In a further communication, placing at its head the 

 following thesis much in the same spirit as Luther nailed 

 his famous theses to the church door at Wittenberg : 

 " Hectocotvlatio bene obscrvata et rite conslderata divisionl- 

 bus naturae semper congruit ; incongrua divlsionibus, eas 

 arbitrarias et factltias esse indicat." 



Steenstrup further explains ihat ihi- point of most conse- 



