ZOOLOGY. 



Bt Theodore Gill. 



INTKODUCTION. 



During the past year no discoveries of previously unknown types of 

 animals of such magnitude as signalized the year 1880 have been made, 

 but much i)rogress has been effected in general morphology and toward 

 the systematic appreciation of many minor groups as well as the char- 

 acteristics of various organs and structures. Investigation has been to 

 a large extent in the same direction as it has tended to for some years 

 past, embryology and minute anatomy receiving probably more new 

 disciples than systematic zoology, but the latter is sure to receive new 

 light tioin such special laborers. A noteworthy work that has been 

 completed during the year — Balfour's Introduction to Comparatice Em- 

 bryology — will undoubtedly encourage as it will certainly facilitate re- 

 search in that held. 



The investigation of the deep-sea faunas has been continued and con- 

 firmation of previous conclusions as to the characteristics thereof has 

 been obtained and supplemented by new discoveries. The i)rotest which 

 we have before made against the association of the deep-sea animals 

 with those of the coast to which they happen to be nearest may be aptly 

 repeated in this connection. There is no more reason, so far a^ the ani- 

 mals tltemnelrea are concerned-^ why for instance we should allocate the ani- 

 mals of the deep seas off the New England coast with the coast-inhabit- 

 ing animals than for bringing the animals of the entire northern Atlantic 

 into the same connection. There is in fact less reason, for there are more 

 si)ecies and more types shared in common by the coast waters of Xorth- 

 eastern America and Northern Europe, than by the former and tlie 

 abyssal depths within a couple of hundred miles of the coast. If it be 

 urged that it isdithcult to draw the line between the different zones, it 

 must be remembered that it is equally difficult to establish the demar- 

 Ciition between contiguous littoral faunas. In a communication on the 

 deep-sea crustaceans, Mr. x\lphonse Milne-Edwards lias called attention 

 to the fact that near the Spanish coast and the Bay of Biscay are two 

 distinct I'aunas neither of which would have been regarded as belong- 

 ing to the same geological period nor to the same climate, and he not 

 unnecessarily cautions geologists against too sweeping assumptions 



40J 



