ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 503 



an Indian club, striped longitudinally with white, and filled to dis- 

 tention with a thin clear fluid. They are not quite equal, nor are 

 they placed symmetrically in the body-cavity, but the one or the other 

 lies between the nervous chain and the ventral body-wall in the 

 middle line between the two rows of vertical muscles, and the other 

 between the row of muscles and the lateral wall of the side of the 

 body to which it properly belongs. They apparently consist of a 

 strong and structureless basement membrane, invested externally by 

 a layer of delicate striped muscular fibres arranged circularly, and of 

 an inner membrane ; the walls of the short (1 mm. long) ducts are 

 transversely thickened so as to resemble the tracheae of insects ; the 

 granular tissue is arranged between the two membranes in longi- 

 tudinal plated stripes, so as to permit of the expansion of the lumen 

 of the tubular organ in a receptacle or bladder for the storing up for 

 use of the secreted fluid, to which apparent arrangement of the 

 granular substance the striped appearance of the organs is due. 



The secretion doubtless serves to protect the animal from attack, 

 and it is interesting to find that the female in this, as in so many 

 other animals which are similarly protected by their offensive 

 odour, is (as being for obvious reasons the more important sex) more 

 perfectly protected than the male by having, not indeed, so far as 

 could be detected, a stronger and ranker, and therefore more disagree- 

 able scent, as in many insects, but larger scent-secreting glands. 

 Another point of interest brought out by this investigation is that 

 the two glands exhibit a tendency to coalesce and form a single 

 unpaired median organ, the two being always unequal and occasionally 

 partially united and the one in the middle line invariably the larger. 



These structures seem to belong rather to the category of excre- 

 tory organs than to be highly developed skin-glands ; and they are 

 probably homologous with the silk-glands of other Arachnida and of 

 Insects, with the green-gland of the Crayfish, and with the segmental 

 organs of Worms and Peripatus. 



5. Crustacea. 



Classification of the Brain of Crustacea.* — Dr. A. S. Packard 

 gives the following provisional grouping of the brain of Crustacea, 

 which he considers to be justified by known facts, although excepting 

 the brains of Decapoda aud Limulus, no special histological work has 

 been accomplished. The terms archi-cerebrum and syn-cerebrum 

 have been proposed by Professor Lankester, the first to designate the 

 simple worm-like brain of Apus, and the second the composite brain 

 of the Decapoda, &c. 



Decapoda. 



Tetradecapoda. 

 Syn-cerebrum ( Phyllocarida. 



Cladocera. 



k Entomostraca. 



iPhyllopoda. 

 Merostomata (Limulus^). 

 Cirripedia ? 



* Amer. Natural., xvi. (1882) pp. 588-9. 



