292 EEVIEW. 



that these lateral eyes consist of simple depressions o£ the epi- 

 dermis, there being no folding in of the edges of the depression so 

 as to form a vesicle, and consequently no duplication or triplication 

 of the layers. The fact thus established, that there is no vitreous 

 layer in certain Arthropod eyes intervening between the cuticle and 

 the nerve-end cells, naturally enough is an obstacle to Dr. Patten's 

 sweeping generalisation. After citing the observations in question 

 he dismisses them with the cool remark : " For theoretical reasons I 

 am obliged to assume that this layer (the vitreous) is always present." 



Were Dr. Patten not dominated by theories, one more extrava- 

 gant than another, he would not have "assumed " anything about 

 such an important matter, but would simply have taken a Scor- 

 pion (common enough at Naples), and cut some sections of its 

 lateral eyes. Dr. Patten, ho*vever, openly professes that he has 

 made it his habit in constructing his views on the structure of eyes 

 to " choose his own course, picking out those facts which seem to 

 point in the right direction ;" that is to say, which support a favourite 

 theory or amplify a startling generalisation, and ignoring or flatly 

 denying, without troubling to bring them to the only test recognised 

 by loyal students of nature, those which cannot be thus used. 



13. Finally, we must point out that, in expressing his opinions. Dr. 

 Patten often shows as great a want of manners as of fundamental 

 knowledge. He objects to the supposition that in more complex 

 eyes some of the pigmentiferous cells are due to intrusive connective 

 tissue which has penetrated between the cells of epidermic origin. 

 One author, he states, " has carried this supposition to an absurd 

 degree." There is nothing "absurd" in the supposition, as Dr. 

 Patten would recognise were he acquainted with the histology of 

 the epidermis. In Lumbricus, Hirudo, and even in some Verte- 

 brates, the occurrence of such intrusive connective tissue is a de- 

 monstrable and admitted fact ; and in relation to the eye of 

 Arthropoda it appears to have been actually observed taking place, 

 according to Kiugeley's recent account of his investigation of the 

 development of the eye of Crangon ('Zoolog. Anzeiger,' No. 234). 

 But in any case it ill becomes a novice to charge his masters and 

 teachers with " absurdity." It should be enough for him to demon- 

 strate an error (if he can) and to employ respectful language in 

 doing so. 



Grenacher is subjected by Dr. Patten to even more objectionable 

 treatment. On p. 728, this young American, after citing an opinion 

 published by Grenacher, says : " This he knows is absurd, and 

 cannot be true." The expression is ofiensive and discreditable. 



On the whole we cannot congratulate Dr. Dohrn on his con- 

 tributor. There are, no doubt, some laborious observations con- 

 tained in this ill-regulated production ; but it is a question whether 

 their value will counterbalance the effect on the author's reputation 

 of the evidence which it bears of his want of both scientific and 

 social education. 



