138 SUMMARY OF CUKRENT RESEARCHES RELATING TO 



clear and typical. The development of these structures is described in 

 detail, and the author goes on to that of the tongue and radula. Special 

 attention is given to the chordoid tissue of the tongue. It seems 

 probable that: the musculature of tin- tongue has a common origin with 

 the columellar musculature, from which also that of the creeping foot 

 is subsequently derived. 



Attention is directed to two transient structures — the " nephrocysts " 

 and the larval heart. The nephrocysts are two very large cells, one on 

 each side of the gullet in the primary body-cavity. The larval heart is 

 a thin-walled portion of the body-wall, in the mantle cavity behind the 

 velum, which pulsates vigorously long before the definitive heart is 

 formed. The invaginated endoderm cells differentiate into stomach, 

 liver, and intestine. The hind part of the intestine appears to be 

 < inlodermic. From the first the primordium of the liver is unpaired 

 and dorsal. 



The sense-organs appear before the nervous system. The statocysts 

 arise from a minute ectodermic proliferation of the epithelium of the 

 foot behind the mouth. Very similar is the origin of the eyes. Between 

 the two lobes of the velum and the apical cell-plate, ou each side of the 

 latter, there is a group of small cells, which retain for a time an embryonic 

 character, and include the primordia of tentacles, eyes, and cerebral 

 ganglia. A detailed account is given of the development of the nervous 

 system. That of the heart, kidney, and gonads is more provisionally 

 described. The shell and the mantle, the torsion and the asymmetry 

 are also dealt with. 



Acroloxus lacustris.* — E. Popple, in recording the occurrence of this 

 fresh-water Gasteropod in Hertfordshire, compares it with the much 

 commoner Ancylus fluviatilis. In the latter the shell is rather round 

 and elevated, the beak blunt and turned to the right. In the former 

 the shell is oblong and depressed, the beak sharp and turned to the left. 

 The usual habitat of Ancylus is on stones in running water, while 

 Acroloxus is generally found on leaves of aquatic plants in still water. 

 •• Apart from the above differences it is found on examining the body of 

 Ancylus fluviatilis that the important organs are situated on the left 

 side, whereas in Acroloxus lacustris they are placed on the right side of 

 the body." In Ancylus there are 120 rows of 37 teeth on the radula, 

 in Acroloxus 75 rows of 3!) teeth. 



Arthropoda. 



Olfactory Sense in Hymenoptera and Spiders. t — N. E. Mclndoo 

 has made numerous experiments with ants, bees, hornets, and spiders in 

 reference to the sense of smell. The odours used were such as oil of 

 peppermint, thyme, winter green, clove, and bergamot. "When the 

 pedipalps of spiders are removed the behaviour remains normal, and the 

 reaction time is -practically the same as when intact individuals are 

 tested. But when the antenna? of Hymenoptera are mutilated in the 



* Trans. Hertfordshire Nat. Hist. Soc, xv. (1915) p. 240. 

 t Smithsonian Misc. Coll., lxiii. (1914) No. 9, pp. 1-63. 



