.8^,. SOME NEW BOOKS. 551 



second edition, but an entirely new work, as is necessary from the 

 great advances in our knowledge of the structure and development 

 of insects during the last twenty years. This first volume deals with 

 the anatomy of the larva, the development of the embryo and of the 

 imago, the external anatomy of the imago, and its histology. There 

 are also chapters on the general life-history of the blow-fiy, the 

 general anatomy and morphology of insects, and the characters of 

 the Diptera. The volume has appeared in three parts, the first 

 issued in October, 1890, the third in April, 1892. In the second 

 volume, which has yet to appear, we are promised " a detailed 

 description of the various internal organs, their development, and 

 physiology." 



The study of insect anatomy has been neglected in this country, 

 and the later literature of the subject has mostly come from the 

 laboratories of Germany and Russia. We have, however, Miall and 

 Denny's excellent monograph of the Cockroach, one of the most 

 generalised of insects. Mr. Lowne's work is much larger than this, 

 his type being a highly specialised insect. 



It is impossible not to admire the thoroughness with which Mr. 

 Lowne has carried out his task, and the laboriousness of his investi- 

 gations deserves every acknowledgment. The plates representing 

 the parts of the exoskeleton of the thorax are striking examples of 

 this, no less than fifty-three sclerites being figured. In his descrip- 

 tion of the structure of the feet, he confirms the oldest suggestion as 

 to the method of walking on plane surfaces : that the hairs on the 

 pads secrete drops of viscid fluid which temporarily attach them to 

 the surface, instead of the later theories that the hairs act as hooks 

 or the pads as suckers. The mechanism at the base of the wing con- 

 sists of several sclerites, and their action in producing the motion of 

 the wing-tip is described. The curve described by the tip is of com- 

 plicated form, and closely agrees with that arrived at for dragon-flies 

 by Lendenfeld by means of instantaneous photographs. 



In his interpretation of the proboscis, Mr. Lowne differs from 

 most insect-anatomists. This organ in the fly has generall}^ been 

 regarded as almost entirely formed by the second pair of maxillae 

 (labium or lower lip) as it undoubtedly is in the Hymenoptera. Mr. 

 Lowne, however, considers that he has evidence, from its structure 

 and development in the blow-fly, that it really represents the first 

 pair of maxillae, and that we must consequently compare it with the 

 sucker of a moth, not with that of a bee. He would derive the 

 rostrum of the Hemiptera from the same source. The labium of the 

 fly he supposes to be quite rudimentary. The piercing stylets which 

 are found in many Diptera, and have always been regarded as the 

 mandibles and the first pair of maxillae, he considers, as well as the 

 sucker, to represent parts of the first pair of maxillae only. The 

 similar stylets in the Hemiptera would probably be explained in the 

 same way. These views will certainly not be accepted without further 

 evidence, but they deserve careful consideration, and will stimulate 

 research. 



An embryological point on which Mr. Lowne is at variance 

 with most other observers is the nature of an invagination in the 

 dorsal region of the blastoderm (dorsal organ of Kowalevsky). This 

 structure, regarded by Graber as the proctodaeum, is thought by Mr. 

 Lowne to be an archenteron, and, therefore, to show a typical gastru- 

 lation. The Malpighiari tubes are developed as sacculi from this 

 cavity ; hence if it is an archenteron, they are coelomic in origin, and 

 show more affinity with the excretory organs of other invertebrates 



