40C) SUMMARY OF CURRENT RESEARCHES RELATING TO 



than the 100,000tli of an inch in diameter." In Zygoma trigonilla the 

 structure is quite different ; there- is no trace of cross-ribbing, but from 

 the inner part of the membranes of the scale Mr. Smith thinks a tufted 

 structure springs, which in appearance is not unlike the hairs on the 

 leaves of some plants. 



Scent-organs of German Lepidoptera.* — Prof. P. Bertkau has con- 

 tinued his observations on the scent-organs of various German Lepidoptera. 

 The Noctuina have vent rally placed organs of the Sphingid type. In 

 Hadena and Dichonia the hairs of the tuft are extraordinarily long ; 

 there is not, as in the SphingidaB, one scale on one large gland-cell, but 

 several smaller cells belong to one sc-ilo. A very similar apparatus was 

 found in some Orthosiid®. It is somewhat remarkable that homologous 

 organs should be found in groups which are, systematically, so wide 

 apart as the Sphingida3, Noctuina, and Geometrida3. 



Scent-glands of Phryganidse.f — Dr. W. Midler has been confirmed 

 in his opinion that the peculiar palpi of Sericostoma personatum were 

 comparable to the scent-glands of Lepidoptera by the discovery that they 

 are confined to the male. Instead of the four elongated joints of the 

 maxillary palp which are found in the female, the male has a single 

 terminal joint formed by the fusion of several joints ; this is almost 

 sjjoon-shaped, the edge which is turned away from the head is widened ; 

 on the other side the spoon lies so close to the head that it seems to form 

 part of it, and covers it like a mask ; by this means the secretion appears 

 to be protected from evaporation. The interior of the spoon is quite 

 filled by very fine hairs, which are pale, faintly knobbed, and about one 

 millimetre in length. When the palpi are separated the hairs become 

 spread out. 



The secondary sexual organs which have been observed in various 

 Phryganids, such as Noticlobia, Drusus, and Grurnicha, are probably also 

 scent-organs. 



Development of Endoderm of Blatta germanica.} — M. N. Cholod- 

 kovsky has undertaken the reinvestigation of the origin of the endoderm. 

 The endoderm in Blatta germanica does not become differentiated until 

 after the closure of the primitive groove, the appearance of rudiments of 

 the appendages, and the beginning of the differentiation of two nerve- 

 trunks from the ectoderm. The inner of the two constituent layers of 

 the embryo breaks up into two rows of hollow mesodermal somites ; the 

 cells of the inner median wall of the somites become distinctly differ- 

 entiated into two layers, the thicker of them form the mesodermal 

 enteric wall, while the other gradually separates itself from the wall of 

 the somite, lies close to the nutrient yolk, and forms the true endoderm, 

 which, later on, completely incloses the yolk. The yolk-cells take no 

 part in forming the endoderm, and appear to be provisional phagocytes 

 in the histolysis of the nutrient yolk. 



The late appearance of the endoderm of Blatta is intelligible when 

 we consider the extremely small part which it plays in the structure 

 of the complete insect, in which the greater part of the organs are of 

 ectodermal origin. 



* Verh. Nat. Ver. Preuss. Ebeinlande, xliv. (1887) pp. 118-9. 

 t Arch. f. Naturgesch., li. (1887) pp. 95-7. 

 \ Zool. Anzeig., xi. (1888) pp. 163-6. 



