ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 35 



accumulated slime-covered particles into the oesophagus. If the foreign 

 particles are not thus ingested, they are sooner or later caught in the 

 marginal stream of the lips and passed along the inferior marginal fringe 

 of the labial palps to their tip, and finally discharged into the efferent 

 backward stream. If the labial palps in consequence of stimulus are 

 drawn together, they usually hinder the food-particles from entering the 

 mouth, and conduct them into the efferent stream. The labial palps in 

 certain states of contraction form the connection between the afferent 

 and efferent streams, and serve to pass material from the one to the 

 other. 



Mechanism of Swimming in Pecten.*— Fred Vies has studied the 

 scallop's swimming movements. The opening of the valves is normally 

 in the direction of progression, the hinge is behind. The movement is 

 due to the reaction to the current of water which passes out by the 

 cardinal grooves, the pallial folds acting as a valve and preventing any 

 other issue of the water when the valves are rapidly closed. 



Genus Joufia Boehm.f — E. Snethlage, from a study of fresh material 

 of Joufia reticulata Boehm, is able to throw some light upon its relation- 

 ships. Externally, and in the structure of its lower valve, it resembles 

 many Rudistfe (Sph^rulites) ; in the outer layers of this valve it exhibits 

 resemblances to Hippurites. It shows least resemblance to the Caprinidge, 

 and should be linked to the groups Radiolites and Hippurites. 



Arthropoda. 

 a. Insecta. 



Cytological Aspect of Parthenogenesis in Insects.^ — C. Gordon 

 Hewitt gives a useful summary of what is known as to the changes which 

 take place in the maturation and development of unfertilised ova in 

 insects. He uses a slight modification of Henneguy's classification :— 

 (1) Tychoparthenogenesis (accidental and exceptional). (2) Homoparthe- 

 nogenesis (normal parthenogenesis), including {a) thelyotoky (only 

 females produced), (&) arrhenotoky (only males produced), and (c) 

 deuterotoky (both sexes produced). {?>) Heteroparthenogenesis (with, 

 alternation of generations). He gives a brief account of the cases in 

 which the cytological changes have been studied. 



Except in Aphis and a few exceptional cases, three polar nuclei are 

 formed, but tliey are not extruded, as polar bodies. This may secure 

 cytoplasmic fertilisation, so to speak. " The evidence available on the 

 cytology of parthenogenesis in insects is too small and too diversified at 

 present to allow us to draw any conclusions on questions of heredity and 

 sex, about which we know little." 



Structure of Insects. § — Antonio Berlese discusses (in part) the 

 structure of the muscular tissue, tegumentary organs, and glandular 



* Comptes Rendus, cxliii. (1906) pp. 611-13 (2 figs.). 



t Ber. Nat. Ges , Freiburg, i. Br. xvi. (1906) pp. 1-9 (2 figs, and 2 pis ). 



X Mem. and Proc. Manchester Lit. and Phil. Soc, 1. (1906) No. 6, pp. 1-40 

 (2 pis.). 



§ Gli Insetti. Milan: Societa Editrice Libraria, i. fasc. 16-17 (1906) pp. 

 457-520. 



D 2 



