ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 713 



INVERTEBRATA. 



Mollusca. 

 7- G-astropoda. 



Adaptive Structure of Acera.* — Remy Perrier and H. Fischer 

 describe some of the peculiarities of this genus. The coils of the spire 

 do not fuse as usual, bat remain free at the sutural margin, leaving a 

 narrow cleft extending round the shell. This cleft is really open only 

 near the mouth of the shell ; in other parts it is covered by an envelope, 

 at first membranous, afterwards calcareous, which secondarily unites the 

 various coils. To the open portion of the cleft there corresponds a deep 

 pallial sinus, with the single aperture of the pallial cavity. These and 

 other peculiarities are shown to be adaptations to a limicolous life in 

 troubled and muddy water. 



Gill of Bulleidse.f — Rcmy Perrier and Henri Fischer describe the 

 structure of the gill in Haminea hydatis. It is remarkable in having 

 only a few sporadic ciliated cells, and even these have weak cilia. The 

 same is true of the mantle generally, but there are two ciliated pallial 

 bands strongly developed, and on their activity the movement of the 

 water in the mantle-cavity depends almost exclusively. 



Double Snail.f — H. M. MacCurdy describes a double specimen of a 

 species of Campeloma. It had two separate dextral shells (10 mm. in 

 diameter) slightly smaller than the average, two opercula, two pairs of 

 eyes, and two pairs of tentacles. To what extent the internal organs 

 were duplicated was not determined. The left side of the foot of each 

 individual was closely united with the left side of the other in such a 

 manner as to bring the forward movements of each individual in more 

 or less direct opposition to the movements of the other. " Locomotion 

 was thus impeded, though the dominating influence of one which was 

 slightly larger than the other always determined the direction of move- 

 ment."" The interesting specimen or specimens lived only a few days. 



Arthropoda. 

 a. Insecta. 



Nesting Habits of Bembex nubilipennis.§ — J. B. Parker describes 

 the behaviour of this large solitary wasp, known in Kansas as the yellow 

 jacket. Though solitary, they nest in colonies. A sloping burrow is 

 made in the ground, and the eggs are laid in lateral chambers. In no 

 case was more than one developing larva found in a burrow. The 

 mouth of the burrow is closed when the wasp leaves or enters the nest. 

 It seems that all burrows with immature larvse are closed up at night- 

 fall with the female inside. A small fly (Tachinid) makes persistent 

 efforts to enter when a burrow is open. The food of the larva consists 

 of house-flies, stable-flies, flesh-flies, and the like. 



* Comptes Rendus, cli. (1910) pp. 248-50. t Tom. cit., pp. 102-4. 



; Rep. Michigan Acad. Sci., xi. (1999) p. 119. 

 § Ohio Nat., x. (1910) pp. 163-5. 



Dec. 21st, 1910 3 b 



