ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 173 



never have compound eyes and are often blind. (2) There are guests 

 of the " Trutztypas" in which the form of the body is not readily 

 gripped, e.g. Cephaloplectini (Xenocephalini) and Pygostenini. Their 

 frequent colour-resemblance to their hosts is probably adaptive to 

 external enemies. (3) There are guests of the " Symphilentypus " 

 which give off a secretion pleasant to their hosts who lick them. 

 (4) There are guests of the " indifferent type" e.g. Myrmedoniu, which 

 retain more or less of the form of their non-dorylophilous relatives, and 

 are connected by incipient and half-way transformations with one or 

 other of the three preceding types. 



In the second part of his communication Wasmann illustrates in a 

 very interesting way the convergence between neotropical and ethiopian. 

 guests of each of the first three types above-mentioned. There is a 

 very striking parallelism, e.g. between Mimeciton and Dorylomimns, 

 between Sympolemon and Ecitoyaster. 



The third part of the paper continues the comparison of American 

 and African forms. Wasmann gives the " palm of mimicry " without 

 hesitation to Mimeciton pulex whose reflection of Eciton-civAYacters is- 

 extraordinary. Some of the African forms are more accurately mimetic 

 as regards thorax-form, e.g. Dorylosthetus, but the ideal of mimicry is 

 to be seen in Mimeciton. Sometimes the mimetic resemblance is " ex- 

 cessive and exaggerated," thus Mimeciton has actually lost facetted eyes. 

 The author has many more notes of great value to the student of 

 adaptations. 



Exuvial Glands in Insects.* — W. L. Tower has carefully studied 

 the structure of the exuvial glands and the formation of the exuvial 

 fluid in the larvae of the Chrysomelid beetle, Leptinotarsa decemlineata 

 Say. He maintains that the exuvial glands are not true glands, but the 

 setigerous cells which, in early life, are chiefly concerned with the forma- 

 tion of the hairs upon the body. Upon the loss of these, the cell takes 

 on the function of secreting the exuvial fluid, which is most copious at 

 pupation. These cells degenerate in the pupa, and take no part in the 

 formation of the imaginal ornamentation. 



Hepatic Function in Insects. f — A. Porta has demonstrated a 

 biliary secretion in Coccinella and he states briefly his conclusion that 

 this occurs (1) in the casca, (2) in the villosities of the stomach wall, 

 and (3) in glands which lie in the wall of the mesenteron between the 

 muscle-strands. 



Excretion in Gnat Larvae. $ — S. Metalnikoff has continued Kowalev- 

 sky's work on the excretory function of the pericardial cells. Carmine 

 introduced into the gut is absorbed by-the large epithelial cells of the 

 mid-gut and passed on into the general cavity of the body. In other 

 words, it passes into the blood. The leucocytes have no part so far. 

 The pericardial cells soon show a rosy colour. They lie on each side of 

 the heart, two pairs on each segment except the first, which has only 

 one. After they have taken in the carmine they begin to break up and 



J * Zool. Anzeig., xxv. (1902) pp. 4G6-72 (8 figs.), 

 t Anat. Anzeig., xxii (190:S) pp. 447-8. 

 X Bui!. Acad. Imp. St. Pctcrsbourg, xvii. (1002) pp. 49-58 (2 p's.). 



