206 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of two parts, which vary in form, while the genital palps are elongated 

 or round, and are always provided with hairs. The several genera 

 examined are described in detail, and some new forms are to be found 

 among the species. 



Enteric Canal of Ephemeridee.* — Herr A. Fritze finds that the 

 digestive tract of the Ephemeridse consists, in all stages of development, 

 of fore-, mid-, and hind-gut. The oesophagus of the larva is spacious, 

 but in the imago it is very narrow, so as to hinder the exit of the air 

 contained in the tract. The mid-gut of the larva has the form of a 

 cylindrical tube which extends from the beginning of the thorax as far 

 as the seventh segment of the thorax ; it consists, histologically, of a 

 strong layer of circular muscles and a high palisade-like epithelium, the 

 cells of which are filled with granular matter. In the imago the muscular 

 layer has disappeared, and the epithelium has become flattened. The hind- 

 gut, which in the larva serves for the passage of the fseces and the secretion 

 of the Malpighian tubes, and in the imago for that of the latter only, 

 is divisible into small intestine, large intestine, and rectum. The first 

 of these portions is, in the imago, converted into a very complicated 

 sphincter, the function of which is to hinder the escape of the air con- 

 tained in the mid-gut. The large intestine has a very peculiar lining 

 epithelium, the function of which is, probably, excretory ; its cells are 

 constantly being destroyed and renewed. 



The enteric canal of the Ephemeridfe is in no stage rudimentary, but 

 is everywhere completely formed histologically ; in the various stages of 

 the development of the animal it alters its function, for while in the 

 larva it serves for purposes of digestion, in the imago it contains air, 

 &c., and serves as a parachute on the one hand, and aids, on the other, 

 the functions of the reproductive organs. This change of function 

 affects its external form and its histological structure ; the metamorphosis 

 occurs in the nymph and subimago stages. Among the species examined 

 were Ephemera vulgata (imago), Bsetis fluminum (larva, nymph, sub- 

 imago, and imago), Cloe diptera (all four stages), and Csenis lactea 

 (imago). 



Lepidopterous Larvee.f — Mr. E. B. Poulton gives, in detail, an 

 account of his observations on Lepidopterous larvae in 1887. He com- 

 mences with complete accounts of the life-history of Sphinx convoluti 

 and Aglia tau. The ovum of the former is remarkable for its extremely 

 small size ; its development is at about the same rate as that of S. 

 ligustri, namely, from eight to ten days. Tn the ontogeny of the latter 

 there are a number of important characters by which it shows itself 

 related to the Sphingidse, and especially to Smerinthus ; these have led 

 the author to consider the natural position of the Sphingidse, and he 

 concludes that there is a large body of evidence in favour of the view 

 that they are a specialization of Saturnian Bombyces. From a con- 

 sideration of the larvae Mr. Poulton concludes that the characteristic 

 Sphinx attitude is to be explained as the combined effect of gravity and 

 of muscular reaction upon the anterior unsupported parts of the body. 

 An account is given of the use of the graphic method of representing 

 the growth of lepidopterous larvae. The means of defence adopted by 

 the larva of Stauropus fagi are next considered ; the irritated larva 



* Ber. Naturf. Gesell. Freiburg, iv. (1888) pp. 59-82 (2 pis.), 

 t Trans. Eutomol. Soc. Loud., 1888, pp. 515-606 (3 pis.). 



