ZOOLOGY AND BOTANY, MICROSCOPY, IITC. 65 



cones, and vase-shaped and cupola-shaped organs. The first fiv(.' huve 

 a tactile sense, especially the tactile papillaj. The last two in the list 

 have to do with a perception of the resistance of the water and tlu- air 

 in swimming and liying. 



The gustatory papillae and the hollow pitted cones have to do with 

 a chemical sense. Taste and smell can hanlly be (IJRtinguished, especi- 

 ally during the life in water. The head bears all forms of mechanical 

 sense-organs. The chemical sense-organs occur on the antenme, on 

 mouth-parts, and about the mouth. The antennui function as efpiili- 

 brating organs. 



The thorax bears all the different types except the tactile papilhe, 

 the gustatory papillog, and the vase-shaped organs. But there are onlv 

 a few hollow^ pitted cones. The cupola-like organs occur only on the 

 limbs. In the female's pronotum there is a denser disposition of the 

 larger sensory structure than on the corresponding region in the male. 



The abdomen bears only tactile organs — sensory hairs, sensory 

 bristles, sensory rods, and solid pitted cones. Chemical irritability is 

 strongest in the head, and grows less posteriorly. The more complicated 

 mechanical sense-organs are absent from the abdomen. In the adult 

 beetle the sensory cells of any sense-organ always appear uniform. 

 Trichogenous and glandular cells could not be distinguished, nor was 

 any ramification of nerves detected. 



(Enocytes of Ephestia.* — Walter Stendell has made a special study 

 of these elements, which occur in almost all insects. In Ephestia kuehn- 

 iella there are two kinds of generations, those which occur in segmental 

 groups in the larva and those which appear shortly before pupation. 

 The latter appear from the second to the fifth abdominal segments, sepa- 

 rating from the hypodermis and forming a uniform layer. Both sets 

 are directly derived from the ectoderm, the first set in close relation with 

 the trachea. Both show the same sort of secretory activity. Drops 

 appear first in the nucleus and then in the cytoplasm, and are finally 

 exuded. The cells are secretory, not excretory. Their role remains 

 obscure, but it is suggested that they are auxiliary to the intense 

 metabolism of the insect development. 



Development of Tog Flea.j — Bruno Harms finds that the duration 

 of the larval development of Ctenocephalus canis is dependent on the 

 temperature, being shortened by a rise. The imaginal disks for the 

 future limbs appear in each thoracic segment as two disk-like masses^ 

 quite separate from the epidermis. They are surrounded by a cell-ring, 

 so that there is no open peripodal cavity. The antenna is a single- 

 jointed cylindrical sense-organ, jointed to an insertion-tubercle, and 

 bearing a strong bristle at its apex. 



The buccal cavity is distinct from the very muscular pharynx. The 

 oesophagus shows six longitudinal ridges and extends to a short distance 

 behind the supra-oesophageal ganglion, passing into the longitudinally 

 plaited crop. At the boundary of prothorax and mesothorax the fore- 



* Zeitschr. wiss. Zool., cii. (1912) pp. 136-68 (1 pi. and 3 figs.), 

 t Arch. Mikr. Anat., Ixxx. (1912) pp. 167-216 (1 pi. and 13 figs.). 



Feb. 19th, 1913 ? 



