Vol. II, Wo. 10] INSECT LIFE. [April, 1890. 



SPECIAL NOTES. 



On the compound Eyes of Arthropods.— Studies from the Biological 

 Laboratory of Johns Hopkins University, Vol. IV, No. 6, contains a pa- 

 per " On the Morphology of the Compound Eyes of Arthropods " by 

 Mr. Sho Watase, which is of interest owing to its bearing on the origin 

 of the compound eyes of insects. 



The principal subject of the paper is the eye of Limulus, but types of 

 the three great groups of Arthropods — Insects, Crustacea, and Arach- 

 nids — were studied, and the results are included in the generalizations 

 at the close of the paper. 



The primitive type of the ommatidium, or visual unit, is traced into 

 a simple open ectodermic pit from which he believes the compound eyes 

 of Arthropods to have developed by a vegetative repetition of similar 

 structures, not unlike what is supposed to have taken place in the for- 

 mation of certain compound organs in other animals, such as the kidney 

 in vertebrates, or the respiratory organs in Lamellibranchs. 



Taking the number of facets as given by Lubbock, the compound eye 

 of the house-fly (Musca) would represent about 4,000 invaginations of 

 the skin, and of the dragon-fly {JEschna) about 20,000, while an ocellus 

 would represent a single pit. 



In an appendix the compound eye of the star-fish is briefly considered 

 and is found to be morphologically strikingly similar to that of an Ar- 

 thropod. Six lithographic plates accompany the paper and admirably 

 illustrate the author's studies. 



More Ohio Notes. — "A Season's Work among the Enemies of the Hor- 

 ticulturist," is the title of a paper by Clarence M. Weed, read December 

 11, 1889, before the Ohio State Horticultural Society and recently issued 

 in pamphlet form by the author. It treats of both iusect and fungus 

 pests and urges the advantage of combining insecticide and fungicide 

 preparations for the simultaneous treatment of both pests whenever 

 possible. The entomological portion of the paper comprises matter for 

 the most part previously published in the bulletins of the Ohio Experi- 



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