REVIEW. 



Patten on the Eyes of Molluscs and Arthropods. 



In the last number of the ' Mittheilungen ' of the Zoological 

 Station of Naples appears an extensive article by Dr. William 

 Patten on the " Eyes of Molluscs and Arthropods." The article 

 contains the record of a number of observations on the structure 

 of the eye in these animals, which appear to be of considerable 

 value and importance. Accompanying the record of facts is a variety 

 of theoretical and speculative statements, which are so extraor- 

 dinary as not only to call for special notice, but are even likely to 

 lead some readers to underestimate the value of the observations. 

 Indeed, the attitude taken by this young and inexperienced 

 naturalist in criticising the work of his predecessors, and in the 

 enunciation of astounding general propositions, of the eccentricity 

 and inadmissibility of which he appears to be altogether uncon- 

 scious, is one which is greatly to be regretted as likely to diminish 

 the weight which would otherwise be attached to his statements of 

 fact, obviously the outcome of industrious investigation. 



A large portion of the memoir deals with the eyes of Mollusca, 

 of which we shall not here say anything further. The most im- 

 portant new result recorded in the memoir is that relating to the 

 essential structure of the compound eye of Arthropoda. Dr. Patten 

 appears to have discovered that Grenacher is wrong in supposing 

 that the cells of the crystalline cones are the matrix cells of the 

 corneal lenses. He has found a distinct layer of epidermic matrix 

 cells, which produce the cuticular lenses, and were entirely missed 

 by Grrenacher. This new layer is therefore the equivalent of 

 the vitreous layer of the monomeniscous Arthropod eye. The 

 crystalline cone cells are, on the other hand, according to Patten, 

 part of the retinal apparatus, and the rhabdom of Grenacher, which 

 forms a sort of stalk to the group of crystalline cone cells, is really 

 formed by them, and is not a cuticular product of the retinula cells 

 of Grenacher, which surround it, and, according to that observer, 

 produce it. Dr, Patten's observations on these points require con- 

 firmation, but appear to be likely to prove correct. As to nerve- 

 endings, his observations are more doubtful, since he has committed 

 himself in a somewhat over-confident manner to a series of specula- 

 tive generalisations on the subject of nerve-endings, for tlie formu- 

 lation of which it is only too obvious that neither his knowledge of 

 facts nor his acquaintance with the work of contemporary histolo- 

 gists qualify him. He objects altogether to the terra "nerve-end 

 cell," and holds that all the cells of the Arthropod ommateum are sup- 

 plied with nerve-fibres, the chief of which are those which, according 



