58 bulletin: museum of compakative zoology. 



preserved ; there are only very scanty traces of cell outlines and these princi- 

 pally in the superficial division. The nuclei are distinct and rounded or oval 

 and much more numerous in the superficial part. 



6. T]u Cover (co.) consists of a layer of scales which differ from any of 

 those hitherto mentioned in form as well as in arrangement. They are 

 greatly elongated and fusiform in outline, with one end blunter than the other. 

 Bv this blunter extremity they are attached to the surface of the central mass 

 and pass upwards from it in a more or less curved direction. Those which 

 are furthest away from the stalk pass at an angle 45° to the surface. The 

 next ones become successively more and more vertical and then begin to slope 

 over to the other side. Those which cover the greater part of the central mass 

 are inclined at an angle of about 30° to its surface, whilst at the stalk end they 

 run almost directly into it. The thinner ends are drawn out into long deli- 

 cate fibrils which curve round and become continuous with a limiting mem- 

 brane forming the boundary of this layer. 



7. The Superficial Connective Tissue (s. c.) is a layer about 0.016 mm. in 

 thickness. It may be divided into three parts, the deeper and the more super- 

 ficial being structureless, whilst the middle one is granular and has nuclei 

 scattered at intervals along it. I have not been able to make out satisfactorily 

 any nervous supply to the central mass in this instance, but it is quite possible 

 that this may exist between the scales and the posterior cup as in other cases, 

 for many of the sections were much broken. The Posterior Organ I have not 

 examined in section. 



Regarding the functions and homologies of the different parts of these or- 

 gans, there is but little that can be said. The central mass I take to be the 

 source of light, and it agrees in position though not in structure with the cells 

 to which Joubin ('93, '94, "95) has ascribed a similar function in Histioteuthis 

 and Histiopsis. 



What I have termed the posterior cup appears to be closely similar to the 

 corresponding part of the organ described by Joubin, and I think there can be 

 little doubt that he is correct in regarding it as a reflector, though it is not ex- 

 actly clear to me that one would naturally expect a body so constituted to 

 discharge such a function. If this be admitted there would then be no reason 

 for doubting that the superficial portions are a refracting apparatus. 



(B ) Abraliopsis hoylei. 



(IMali- lO, Figs. 1-10.) 



The luminous organs of this «j>ecies are exceedingly numerous and are dis- 

 tributed pretty freely over the ventral surface and to some extent over the 

 sides of the mantle, head, and tliird and fourth pairs of arms. Their arrange- 

 ment is almost exactly bilaterally symmetrical with insignificant variations 

 liere and there. Considered more iu detail, the disposition on the various 

 organs is na follows : — 



