ZOOLOGY. 499 



doubtless other conditions, such as presenceof gulf weed, also have their 

 influence." 



The littoral species or " those found in moderately shallow water not 

 far from the coasts, whether they be active swimmers, like Loligo, or more 

 sedentary, like Octopus, are much more restricted in their range than the 

 oceanic." Such have been referred to a number of regions, which agree 

 very closely with those proposed by Dr. Paul Fischer, in his recent 

 " Manuel de Couchyliologie," based upon a study of all the mollusks. 

 Seventeen regions of this character are admitted, and the species, so far 

 as known, are distributed in the following manner: Confined to one 

 littoral area, 199 species ; common to two littoral areas, 27 ; to three lit- 

 toral areas, 12 ; to four littoral areas, 4 ; to five littoral areas, 1 ; to six 

 littoral areas, 2 ; to ten littoral areas, 1. From these indications it ap- 

 pears that 80 per cent, of the species, so far as known, are confined to 

 one area, " a striking confirmation of the proposition that littoral 

 forms in general belong to many species, each of which is confined 

 within narrow limits." The oceanic types are also limited in their dis- 

 tribution, as will appear from the exhibit tabulated by Mr. Hoyle. From 

 one oceanic area, G6 species are known ; from two oceanic areas, 15 ; from 

 three oceanic areas, 3. In fine, " about 75 per cent, of the oceanic forms 

 are confined to one ocean, and cosmopolitan forms must be regarded as 

 exceptional." 



Finally, " thirty-five species are recorded from both oceanic and lit- 

 torai regions, but the majority of these are typically pelagic, and hence 

 their occurrence in the latter areas must be regarded as accidental. 

 Furthermore, it will be seen, that almost without exception, the littoral 

 regions where a species has been found are those bordering upon its 

 proper ocean, which is precisely what would have been expected." 



PROTOCHORDATES. 



Tunicates. 



TJie relations qf the tunicates. — The mooted question as to the rela- 

 tionships of the tunicates, and especially the degree to which they are 

 connected with the vertebrates, has been again discussed. This has 

 been done by Messrs. E. Van Beneden and C. Julin in a memoir on 

 the morphology of the animals of that class. For knowledge of the de- 

 tails we must refer to the original memoir and to the full abstract in 

 the Journal of the Royal Microscopical Society. In this place the sug- 

 gestions as to the systematic position of the group can alone be consid- 

 ered : 



(1) The Urochordata or tunicates form, in connection with the Cepha- 

 lochordata (^. e., Branchiostoma) and Vertebrata, a single primary 

 group — the Chordata. 



(2) " The tunicates have, like the other two divisions, arisen from seg- 

 mented enteroccelous organisms, like the archiannelid worms. Animals 



