884 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Systematic Position of Pulicidse.* — K. Krapelin finds that there 

 is a certain parallel between the buccal organs of the fleas and of the 

 higher Ehynchota, while their other anatomical characters show that 

 the fleas are less closely allied to the Diptera than to the Ehynchota ; 

 they cannot, however, be placed with them in the same order, and it 

 is necessary to form a separate division, for which Latreille's name of 

 Siphonaptera may be used ; their sucking tube is formed by a dorsal 

 and two lateral channels (labrum and mandibles), the anterior portion 

 is alone inclosed laterally by the multiarticiilate palpi of the labium, 

 and, at the base, besides the latter, by the lamelliform palpigerous 

 maxillae. While in both Diptera and Ehynchota the efferent 

 salivary duct is unpaired, there are two in the Siphonaptera ; there is 

 no sucking stomach, or pair of hal teres as in the Diptera, there are no 

 wings, as there may be in the Ehynchota ; there are no facetted eyes, 

 as in the Diptera, but the metamorphosis is complete whereas it is 

 usually incomplete in the Ehynchota. 



-y. Araclinida. 



Development of Spiders.f — W. Schimkewitsch's chief results are 

 as follows : — The cells produced by the cleavage of the egg do not all 

 form pyramids radiating outwards from a central cavity ; some remain 

 within the latter and fill it up ; each " pyramid " contains several 

 protoplasmic masses and is homologous with a polynuclear cell ; each 

 pyramid, as Ludwig has shown, is separated into two layers, one form- 

 ing the primitive ectoderm, the other the primitive endoderm. The 

 cells of the ectoderm collect into a mass on the ventral surface of the 

 egg, the cumulus primitivus ; later the mesoderm arises from a region 

 of the ectoderm which corresponds to the primitive streak ; in front of 

 the cumulus is the blastoporic aperture ; the mesoderm arises from 

 the endoderm as well as from the ectoderm. The mesenteron is at 

 first a closed sac, its cavity filled with the primitive endoderm cells ; 

 two ingrowths take place into the mesenteron dividing it into two 

 cavities ; the upper of these is the cavity of the heart, the lower that 

 of the mesenteron in a more restricted sense ; the blood-corpuscles 

 are partly endodermic and partly mesodermic ; and in the adult there 

 are two forms of blood-corpuscle. The aorta is formed by a cutting-off 

 of the dorsal section of the gut. 



With regard to the appendages, the upper lip is derived from two 

 rudiments erroneously described by Kronenberg as antennsB; the 

 lower lip similarly arises in two portions. Both unite to form the 

 rostrum which corresponds to that of the Pycnogonida. The nervous 

 system originates as two distinct cords from the ectoderm, these 

 approach each other and include an invagination of the ectoderm, 

 which, however, plays an unimportant part in the formation of the 

 nervous system. 



* Festschrift z. 50-jahr. Jubilaum d. Kealgymnasiums d. Johanneums, 

 Hamburg, 1884. Cf. Ann. aud Mag. Nat. Hist, xiv. (1884) pp. 36-53 (1 pi.), 

 t Zool. Auzeig., vii. (1884) pp. 451-3. . 



