ZOOLOGY. 773 



or to the anti-peduncular pole of the ovary, and that it is between the 

 cement-glands, in the sagittal plane, and perhaijs slightly towards the 

 cloaca and the cement-glands, that we must direct the forceps and the 

 scalpel. It is only by the study of a type in which the cement-glands 

 moy be far removed from the mesentery and the cloaca that we can see 

 Avhether the nervous ganglion would entirely break off its relations 

 with the latter two organs and follow the cement-glands in their dis- 

 placement. {Comptes Rendus Acad. Sci. Paris, 1885, p. 1010; Ann. tfi 

 Mag. Nat. Hist. (5), v. 15, pp. 495-498.) 



Blind sessile-eyed crustaceans. — The structure of the brain in sessile- 

 eyed crustaceans, and especially that of the Asellus communis and Ce- 

 cidotaea stygia, has been investigated by Prof. A. S. Packard. The 

 brain of such forms has not ganglion and cells with a simple nucleus, as 

 does that of a lobster and other stalk-eyed crustaceans, but ten to twenty 

 nuclei appear to a cell. The brain is therefore far less complicated than 

 that of the stalk-eyed crustaceans and is " a syncerebrum, the compo- 

 nents being the brain proper or pro-cerebral lobes, the optic ganglia, and 

 the first and second antennal lobes," and these lobes are quite separate 

 from each other. 



As to the blind species Professor Packard thinks that " the steps 

 taken in the degeneration or degradation of the eye, the result of the 

 life in darkness seem to be these : (1) the total and nearly or quite simul- 

 taneous loss by disuse of the optic ganglia and nerves ; {2) the breaking 

 down of the retinal cells; (3) the last step being, as seen in the totally 

 eyeless form, the loss of the lens and pigment." Professor Packard 

 considers this evolution to be explicable upon what may be called 

 "Lamarckian" principles. {Mem. Nat. Acad. Sci., v. 3, part 14, p. 5.) 



Insects. 



Extinct myriopods. — As a result of a study of the fossil myriopods, 

 Mr. Samuel H. Scudder has admitted two extinct orders. The Archi- 

 polypodous type is the oldest, and Mr. Scudder considers that there is evi- 

 dence that some of the Carboniferous forms were amphibious. The group 

 culminated in the Carboniferous, and does not appear later than the 

 Dyas, while with one doubtful exception no true diplopod is know to be 

 older than the Oligocene. The Archipolypoda, which resembled the 

 Diplopoda in having two pairs of legs to every segment, became extinct 

 in the Palaeozoic epoch. Three families have been recognized, the 

 Archidesmidae, Euphorberiidae, and Archijulidae. Another extinct type 

 is found in the Protosygnatha, which are characterized by the develop- 

 ment of only a single pair of legs to each segment, in which respect a 

 resemblance is manifested to the Cliilopoda. One genus only, Palae- 

 ocampa, is known from the Carboniferous. 



For a brief period after leaving the eggs, modern Diplopods and pau- 



