HABDWICKE'S SCIENCE- GOSS IP. 



205 



l'ected growth of the discs of the segments to which 

 they belong, so I believe do the organs in question 

 result, that of the superior prothoracic discs with 

 which they correspond, and the spiracles of the fly 

 as the imaginal appendages with the formation of 

 which these discs are especially concerned. I may 

 as well mention that I have noticed two minute 

 nipples on the prothorax of the pupa-skin of the 



Fig. 134. The certbeilurn ani nerves attached from beneath : 

 c, the cerebellum ; pp, the peduncles connecting- it with 

 the cerebrum; th, the first thoracic ganglion; md md, 

 nerves to the roots of the mandibles ; md' md', branches to 

 the muscles of mandibles; ir,x mx, nerves to maxillae ; mt 

 mt, those to the mentum ; sd sd, branches to muscles of 

 salivary duct, slightly magnified. 



Fig. 135. Cellular structure found beneath the abdominal 

 integument of advanced larva, believed to be the future 

 pupa skin, x 350. 



Fig. 136. Interior prothoracic imaginal disc, showing the 

 coxae at c, the femora at/, and tarsi at t, x 50. 



Blow-fly, which I take to be the homologues of the 

 organs just mentioned, though here they are quite 

 rudimentary. 



Fij 



137. The cephalic imaginal discs : , optic ; a, antenna], 

 with nerves attached, x 50. 



In conclusion I must notice some peculiar organs, 

 the nature of which I do not at all understand. 

 They consist of minute capsules filled with a granu- 

 lar fluid, and are situated in pairs, one pair on the 

 dorsal and the other on the ventral surface of each 

 body-segment, from the third to the tenth inclusive, 

 immediately beneath the skin, through which they 



can be seen when the latter is sufficiently trans- 

 parent. In the foregoing pages I have endeavoured 

 to record such facts as have^'come under my notice, 

 aud in some cases the conclusions to which I believe 

 they lead. The facts may, and probably have been, 

 much better described , before, and both facts and 

 conclusions may contain errors which I would wil- 

 lingly see rectified ; my object, however, will be 

 accomplished if any of my readers will be suffi- 

 ciently interested to examine the subject for them- 

 selves, and form their own conclusions thereon. 



Fig. 138. The cephalic, thoracic, and first abdominal ganglia, 

 with the inferior and superior thoracic imaginal discs, the 

 former connected by nerve -trunks with the thoracic 

 ganglia : cr cr, the lobes of the cerebrum connected by 

 peduncles withe/, the cerebellum; t r/",thepro-,meso-,and 

 metathoracic ganglia ; a, the first abdominal ganglion ; 

 ip sp, the inferior and superior prothoracic imaginal discs ; 

 in. sm, those of the meso-thorax ; im' sm', those of the meta- 

 thorax. 



MICROSCOPY. 



Atlas der Diatomaceenkunde.-— Parts IV. 

 and V. of this work are now published. The author 

 has thus far kept to the promise that six parts 

 would be published in twelve months; the sixth 

 part is to appear in September. Plate 13 continues 

 the pandriform group of Navicula, of which forty- 

 nine figures are given. Plates 14, 15, 1(3, 17, and IS 

 are devoted to the genus Campylodiscm, and contain 

 118 figures, some of them representing forms of ex- 

 quisite beauty. Plates 19 and 20 represent twenty- 

 five varieties and species of Surlrella, most of them 

 belonging to the Fastuosa group. One of these, 

 S. sends, from Campeacliy Bay, represents one of 

 the largest forms of this genus. The author inclosed 

 a circular with the fifth part, in which he alludes to 

 the promised list of figures corrected and enlarged, 

 to replace those that have accompanied the issue of 

 the plates, and he earnestly requests all who are 



