206 SUMMARY OF OUKEENT RESEARCHES RELATING TO 



Hubrecht has discovered that Proneomenia has a radula and odonto- 

 phore. In the division of the Anisopleura, Spengel's group of 

 Streptoneura, or those in which the nerve-cords share in the torsion 

 of the body, is adopted, and it is divided into the Zygobranchia, in 

 which the organs of the left side do not undergo atrophy — such are 

 the limpet (with regard to whose anatomy much information is given), 

 Haliotis, and Fissurella ; the second order is that of the Azygobranchia 

 in which the left ctenidium and nephridium are atrophied ; they are 

 either creeping forms (Eeptantia) like Turbo, Turritella, Gyclostoma, 

 Dolium, Conus, and Buccinum, or Natantia like Atlanta and Ptero- 

 tracJiea. Spengel's name of Euthyneura is also adopted for those 

 Anisopleura in which the tension of the visceral hump does not 

 affect the nerve-cords; here we have the Opisthobranchia and the 

 Pulmonata. 



Although the different members of the group of the Cephalopoda 

 differ very greatly among themselves, they are all characterized by the 

 " encroachment of the fore-foot so as to surround the head, and by 

 the functionally important bilobation of the mid-foot. Following the 

 example of his predecessor (Owen) Lankester enters into great detail 

 as to the structure of the Pearly Nautilus. 



Various observations of general interest occur throughout the 

 article ; the most important is perhaps the description of the nature 

 of the so-called proboscids ; the different forms are described and 

 supplied with characteristic designations ; indeed the whole essay 

 teems with suggestions of new terms. 



It will be noticed that the author now removes the Polyzoa and 

 Brachiopoda from the Mollusca, being led especially by the observa- 

 tions of Caldwell on Phoronis to think that the supposed agreement 

 of structure is delusive. 



Intertropical Deep-Sea Mollusca.* — P. Fischer, working at the 

 collections lately made by the ' Talisman,' finds Arctic molluscs at 

 great depths in the intertropical regions of the Atlantic, and points 

 out that the difference between the superficial and the deep fauna is 

 such that the genera are different, that their reciprocal associations 

 have no relation, and that if the remains of these faunae, although 

 contemporaneous, were to be fossilized, we should say that they 

 belonged to different epochs or represented the population of two 

 distinct seas. With the northern species are found forms that are 

 unknown at present in the northern seas. 



As Loven suspected would be the case, it was found that the 

 bathymetrical limits of the northern forms increased as the equator 

 was approached, and it would appear, therefore, that the temperature 

 of the water has more to do with the distribution of marine animals 

 than the intensity of light. 



A number of forms hitherto supposed to be peculiar to the Medi- 

 terranean, were found off the coast of Africa ; and we may conclude 

 t hat the number of species confined to that sea are small. 



The great depths of Antarctic seas must now be investigated. 



* Comptes Rendus, xcvii. (1883) pp. 1497-9. 



