542 Miscellaneous. 



On the Coloration of the Optical Elements in Locusta viridissima. 

 By M. J. Chatin. 



The authors who have treated of the structure of the eye in the 

 Arthropoda, as also in the Invertebrata generally, have contented 

 themselves with mentioning the existence of a pigment of variable 

 tint, constituting the fine partitions which separate the bacUlar 

 elements ; as to the coloration proper to the latter, it has been mis- 

 understood or regarded as accidental. Former investigations*, how- 

 ever, have enabled me to insist upon the importance of this character, 

 the constancy of which the observation of certain Crustacea showed 

 me, and of which Boll's researches soon afterwards fijxed the value. 



On recently examining repeatedly the eye of an insect very 

 favourable to such studies, Locusta viridissima, Linn., I found ar- 

 rangements which, as will be seen, deserve to be correlated with 

 the facts to which I have just alluded. 



The optical bacilli present the aspect of slender filaments in their 

 lower portion, sensibly dilated in their upper region (near the cone); 

 these filaments are contained in brown sheaths, formed by the pig- 

 mentiferous tissue mentioned above. If, by means of suitable 

 reagents (alkalies &c) and by gradual solution, we succeed in 

 breaking the web of this tissue, the bacilli appear out of their 

 sheaths of a fine tender rose-colour. This tint, which is lively in 

 the eye excised from the living animal and immediately observed, 

 soon gradually becomes weaker, whilst the bacUlus imdergoes a 

 granular alteration; it persists, however, longer at the periphery 

 than towards the central region. 



This description, which is a summary of the essential details, 

 suffices to show that the bacilli of the Locusta present, in their 

 intimate constitution, great similarity to the same parts studied in 

 the Crustacea ; their proper coloration is the same in these difi'erent 

 types, and seems thus to tend towards a generalization of which I 

 hope soon to be able to furnish further examples, and [the interest 

 of which it is unnecessary to point out. — Comptes Hendus, August 

 20, 1877, p. U7. 



On a new Marsupial from Australia. 

 By Prof. R. Owen, F.E.S. &c. 



I have received from Australia skins of a male and female small 

 marsupial, combining the dentition of a Hypsiprymnid or kangaroo- 

 rat, with a hind foot of five digits, a small prehensile hallux (i.) 

 being superadded to the four other digits, of which n. and iii. are 

 long and slender, rv. and v. of the greater length and strength cha- 

 racteristic of the Poephaga. For this interesting form I propose the 

 generic name Pleopus, in reference to the full or type mammalian 

 number of the toes of the hind foot, with the specific name nudicau- 

 datus, from the nude scale-clad tail. Figures of the species will be 

 added to the ftiller account proposed to be given elsewhere. 



* L'Institut, 1876, pp. 125 & 189. 



