634 SUMMARY OP CURRENT RESEARCHES RELATING TO 



logically correct. Analogous cases may be cited from Kiikentliars 

 observations on lymphoid cells in Annelids and Semen's studies on 

 Holothiu'ians. 



In the third and last place the author dfscribes some points in the 

 development of the wing of Lepidoptera. The eversion of the wing in 

 the passage of the larva into the pupa stage is effected by blood-pressure. 

 In the young pupal wing there are, in addition to the large tracheaB, 

 blood-C( rpuscles which are more or less chargi^d with nutrient mater al. 

 It is important to note that the matrix of the trachi se gradually dis- 

 appears altogether, and that in the wing of the imago even the very 

 d' l.cate intima can no longer be found. Scales and hairs are formed on 

 the first day of the pupal stage; both structures are, in general terms, 

 outgrowtLs of greatly magnified liypodermis cells. The mother-cells of 

 the 1 airs are much larger than those of the scales. 



The fusion of the wing membranes begins at a very early stag^, and 

 in a peculiar manner. Clefts appear in the hypodermis owing to the 

 cells increasing in length, and separating from one another. A con- 

 tinuous m mbrane formed of protoplasm is present, which ri^ay be called 

 the ground membrane of the epithelium. Both blood-corpuscles and 

 blood fluid make their way through this membrane. Between the 

 two wing membranes is a sys'em of pillars formed by the hyj)odermis. 

 The clefts in the hypodermis function as blood-spaces, and the fluid 

 clearly serves to nourish the hypoderinis ( f the wing. 



Later on, the two wing membranes are, in consequence of the con- 

 siderable growth of their surface, arranged in a number of small folds. 

 The median membrane formed by tbe fusion of the two is absorbed so 

 that the wing is traversed by a number of thin pillars which connect tbe 

 two membranes. In the imago the hypodermis of the wing is reduced 

 in a extraordinary manner, while the mother-cells of the scales have 

 almost completely disappeared. Tracheae too are no longer to be found. 

 The cuticle » f the wing does not appear till a comparativi ly late stage, 

 and its appearance sets a limit to the growth of the suiface of the wing. 

 The wing-ribs, as Semper calls the tubes which accompany the trnclieas 

 in the veins of the wings, are, the author has observed, connected with 

 the trachege. A rib, when complete, has in cross section the form of a 

 tube which is generally cylndr.cal. and is lined by a very thin chitinous 

 intima, which carries delicate tracheal branchlets. In the ribs there is 

 a Central cord wh:ch in longitudinal section exhibits a distinct longi- 

 tudinal striation; this cord appears to be excreted by the cells of the 

 •wall of the tube, and does not appear to be, as Semper has supposed, 

 nervous in nature. 



Before the wing gets its characteristic marking, owing to the 

 differentiation of the scales, it is coloured red by a pigment deposited 

 in the cells of the hypodermis. The characteristic marking appears in 

 a very short time, and is, therefore, difficult to investigate. The study 

 of these markings has not as yet enabled the author to make out 

 definitely the ph^logenetic development of colour-pattern in the way 

 effected by Weisuiann for caterpillars, and by Eimer for Vertebrates; a 

 few points, however, appear to be indicated. 



Number of Polar Globules in Fertilized and TJnfertilized Eggs 

 of Bees.* — Prof. F. Blochmann has recognized the importance of 



* Morphol. Jahrb,, xv, (1889) pp. 85-96 (1 pi.). 



