586 



darf nach vorn gerichteter Sprossen ist leichter aus dem Bereich der 

 normalen Vordersprossen zu decken, als aus dem Gebiet der ursprüng- 

 lichen Hintersprossen, die in sehr weitgehender Weise (über 90° hinaus) 

 hätten gedreht werden müssen. 



Zoologisches Institut der Forst- Akademie Hann. Münden, 3. Juli 1913. 



2. Note on the Hectocotylized Arm of the Pacific Form of Ommastrephes 

 0. sloanei sloanei Gray. 



By C. Ishikawa, College of Agriculture, Tokyo Imperial University. 



(With 4 figures.) 



eingeg. 7. Juli 1913. 



Pfeffer in his great work on the Oegopsid Céphalopodes^, writes 

 about the hectocotylized arm of Ommastrephes pacificiis as follows: 

 "Der Hectocotylus dieser Form ist noch nicht beschrieben, da nach 

 Würker sich im Münchner Museum 3 Männchen befinden, so ist die 

 Beschreibung in absehbarer Zeit zu erwarten". 



As however the expected description of the Munich specimens has 

 not appeared after the lapse of three years, and as the new Catalogue 

 of Japanese Cephalopoda by S. Stillman Berry 2, does not mention 

 anything about it, I venture to give a sketch of the hectocotylized arm 

 of this species, leaving a fuller description to my monographic work on 

 the Oegopsid Cephalopoda of Japan which is now in preparation. 



The hectocotylization is observed on the right ventral arm as in 

 other species of the genus. In the proximal three-fourths of the arm 

 no difference whatever is to be observed between the right and the left 

 arms, with the exception of the supporting bars of the membrane which 

 on the right are a little longer and somewhat more developed. The 

 distal portion of the arm becomes flattened on the outer side, and forms 

 a broad membrane, and the suckers which are placed along the median 

 dorsal side come to be situated along the inner edge. On the inner 

 row of suckers the transverse bars as well as the membrane supporting 

 them are well developed, while on the outer row the bars and the 

 supporting membrane become rudimentary as we proceed more distally, 

 but the peduncles of the suckers persist to the extreme end of the arm, 

 and become relatively larger and more or less flattened. On the inner 

 row, the peduncles of the suckers become rudimentary in larger specimens. 



To take a concrete case, in a specimen from Misaki with the mantle 

 length of 250 mm. marked (S 12) (Fig. 1) in the collection of the College 

 of Agriculture, there are twenty-one rows of suckers on the proximal 



1 G. Pfeffer, Die Cephalopoden der Planktonexpedition; Ergebnisse der 

 Planktonexpedition der Humboldt-Stiftung; Bd. II, F. a., 1912; P. 57. 



2 S. Stillman Berry, A Catalogue of Japanese Cephalopoda; Proc. Acad. 

 Nat. Sci., Philadelphia, July 1912. 



