Miscellaneous. 73 



site ; if there are three, it is the last alone that is composite. 

 3, The number of abdominal ganglia varies from one to eight ; and 

 the Muscidoe Calypterae have no separated abdominal ganglia, these 

 being confounded with the central nervous part in the thorax. 

 Sometimes the number of abdominal ganglia varies in the same 

 species, according to the sex : according to Landois, Pulex canis has 

 eight and seven ; according to my own researches this is the case 

 also in P. felis and P. irritans. I have also found that in the male 

 Leptis the last ganglion has a constriction, whilst in the female it is 

 compact. 4. The Diptera have a frontal ganglion and two pairs of 

 small pharyngeal gangha ; but they have not the abdominal part of 

 the sympathetic system distinct. 



The nervous system of the Hemiptera has been very little investi- 

 gated, and comparative studies are wanting. My researches on the 

 nervous system of the Hemiptera extend to seventy species. 



1. Some Hemiptera have no separate suboesophageal ganglion, the 

 latter being amalgamated with the medullary part of the thorax. 



2. In some (Pseudoj^hanus) it is separate, and placed, not in the 

 head, but in the thorax. The convolutions of the cerebroid lobes are 

 never wanting. 3. In some Hemiptera which have two ganglia in 

 the thorax, the first results from the fusion of the first thoracic gan- 

 glion with the suboesophageal ganglion. 4. The number of thoracic 

 ganglia varies from one to three : thus Hydrometra, Acanthia, and 

 Mepa have one ; two occur in Pentatoma, Lyr/ieus, &c. ; there are 

 three thoracic ganglia in Pedicuhis, but, having no commissures, 

 they are in contact. Notonecta j^resents an intermediate form, 

 having only a single true thoracic ganglion, which, however, pos- 

 sesses a very strongly-marked constriction. 5. The Hemiptera 

 never have separated abdominal ganglia, they being amalgamated 

 with the thoracic part of the nervous system. — Comptes Remlus, 

 -December 6, 1880, pp. 935-937. 



Habits of a Fish of the Family Siluridae (Callichthys fasciatus, Ciiv.). 

 By M. Caebonnier. 



I have in my possession several individuals of the species called 

 Callichthys fasciatus, Cuv., coming from the river Plate. This 

 species is characterized by two barbels at each angle of the upper 

 lip, two rows of broad and strong scaly plates, which cover the flanks 

 and intercept the lateral line, and two dorsal fins, of which the 

 second (adipose) is furnished like the first with an osseous ray. 

 These fishes, as I have ascertained, come frequently to take in a 

 provision of air at the surface of the water ; but their most inter- 

 esting peculiarity consists in their mode of copulation and repro- 

 duction. 



At the moment of fecundation the female brings together her 

 ventral fins, after the fashion of two open fans united by their 

 edges, and thus forms a sort of cul-de-sac, at the bottom of which 



Ann. & Mag. N. Hist. Ser. 5. Vol. vii. 6 



/ 



