ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 433 



Aphides. In the complete adaptation of the females to the parasitic 

 mode of life we may find a parallel in certain Crustacea. 



Morphology and Anatomy of the Coecidse.* — In a subsequent 

 essay, Dr. E. Witlaczil treats of the morphology and anatomy of the 

 Coecidse. He commences with an account of their metamorphosis ; the 

 larva, when it escapes from the egg, is ■ more delicate than in later 

 stages, and males are scarcely to be distinguished from females ; in 

 later larval stages the female is, as a rule, broader and plumper ; as 

 in allied groups, the female undergoes only an incomplete meta- 

 morphosis, while that of the male is almost complete. Metamorphosis 

 does not take place, as Bouche stated, in a special web, but in the 

 ordinary shield ; the traversed statement appears to owe its origin to 

 a misunderstanding of the investment, which is formed by wax- 

 hairs, having been taken for a web formed by a spinning gland. During 

 development the digestive apparatus undergoes retrograde metamor- 

 phosis, and the intestine degenerates ; in consequence of this the 

 larvae are, in their two later stages, quiescent. The rudimentary 

 antennae and legs are cast off, and quite new organs are gradually 

 formed by the hypodermis ; in place of the one pair of small, two pairs 

 of larger but simpler eyes are developed, and with their appearance 

 the brain becomes larger. 



The unicellular dermal gland produces secretions of far more 

 various kinds than in the Aphides, or even in the Psyllidae ; they 

 most often cover the animal and its eggs, and so act as defensive organs. 

 Wax is not secreted at first ; when it begins to appear it does so at 

 the anterior and hinder edge, but soon spreads over the whole 

 periphery of the body ; the filaments are generally quite thin, are 

 wavy, looped, or zigzag in arrangement. These filaments make a 

 common mesh, and so give rise to the shield, which is generally much 

 larger than the body. 



The tracheal system, which is carefully described, agrees generally 

 with that of the Aphides, Psyllidge, &c. ; the inconsiderable lumen of 

 the stigma is still further narrowed by chitinous processes; the 

 tracheal system of the Chermetidae is noticed, and is stated to be very 

 like that of the Aphides, while it approaches that of the Coccidae in 

 the diminution of the number of stigmata. 



The generative organs of both Coccidae and Chermetidae are 

 described ; in the latter the parthenogenetic females of (Jliermes ahietis 

 give rise to two colour varieties, one of which is bright yellow, the 

 other almost black ; their eggs are developed in the same way as in 

 the Aphides, but take a rather longer time (about a month). The 

 sucking-apparatus of the Coccidae and of the Chermetidae closely 

 resemble that of the Aphides ; the digestive organs of the former have 

 been well described by Mark ; the two groups approach one another 

 by the possession of multilobate salivary glands and both differ from 

 the Aphides in having a sack at the base of the labium, which is 

 formed by the hypodermis, and has thin but somewhat strongly 

 chitinized walls. 



* Zeitscbr. f. Wiss. Zool., xliii. (1885) pp. 149-74 (1 pi.). 



