ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 525 



each ring-like segment or somite of the body, and some of these are in 

 all cases retained as gonoducts and often as renal excretory organs 

 (green glands, coxal glands of Arachnida, but not crural glands, which 

 are epidermal in origin), while true nephridia, genetically identical with 

 the nephridia of earthworms, do not occur. 



Prof. Lankester proposes and gives justification for the following 

 arrangement of the larger sub-divisions of the Arthropoda : 



Grade A. Hyparthropoda (hypothetical forms connecting ancestors 



of Chajtopoda with those of Arthropoda). 

 Grade B. Protarthropoda. Class Onychophora, e.g. Peripatus. 

 Grade C. Euarthropoda. Class 1. Diplopoda, e.g. lulus. 



Class 2. Arachnida. 

 Grade a. Anomomeristica, e.g. Phacops. 

 Grade b. Nomomeristica. 



(a) Pantopocla, e.g. Pi/cnogonum. 

 (ft) Euarachnida, e.g. Limulus, Scorpio, My gale, Acarus. 

 Class 3. Crustacea. 

 Grade a. Entomostraca. 

 Grade b. Malacostraca. 



Class 4. Chilopoda, e.g. Scolopendra. 

 Class 5. Hexapoda (= Insecta Pterygota). 

 Incertae sedis : Tardigrada, Pentastomida?. 



The author discusses the segmentation of the body of Arthropods, 

 formulating twelve laws of metamerism ; the theory of the Arthropod 

 head ; the segmental lateral appendages or limbs of Arthropods ; the 

 branchiae ; the eyes ; the tracheje ; the malpighian tubes ; and so forth. 



He then passes the groups of the Arthropoda in review, characteris- 

 ing them so as to indicate their probable affinities and genetic history. 



In an interesting appendix, not contained in the " Encyclopaedia " 

 article, the author discusses the movements of the parapodia of Peri- 

 patus, Millipedes, and Centipedes. 



a. Insecta. 



Moulting Processes in Insects.* — W. Plotnikow describes (1) the 

 separation of the old cuticle from the hypodermis ; (2) the exuvial 

 fluid ; (3) the formation and structure of the new cuticle ; (4) the 

 development of the exuvial hairs ; and (5) the actual process of throw- 

 ing off the old cuticle. In the second part of his memoir he discusses 

 Verson's glands in Lepidoptera, and the exuvial glands in the larvae 

 of Tenebrio molitor, of Chrysomelidas, of Coccinellidae, of Tenthe- 

 dinidse, etc. 



Accommodation-apparatus in Compound Eyes.f — Pierre Vigier 

 notes that each ommatidium of a compound eye includes (1) a dioptric 

 apparatus of refractive elements, which alter the direction of the 

 incident rays ; (2) a receptive apparatus, which receives the luminous 



• Zeitschr. wiss. Zool., lxxvi. (1901) pp. 333-66 (2 pis. and 6 figs.). 

 t Comptes Rendns, cxxxviii. (1904) pp. 775-7. 



