208 SUMMARY OF CURRENT RESEARCHES RELATING TO 



these porous partitions, but they may not be imj)ervious to the fluid 

 portion of the blood. They serve to guide the currents of blood and 

 to cause it to circulate in the appendages. It is not necessary for 

 these i^orous partitions to extend into the apical joints of each ap- 

 pendage, the blood which fills these joints not needing rapid changing. 

 Cams notes that, in the larva of Ephemera vulgaris, the blood has a 

 distinct outward and return current in the basal joint of each antenna. 

 This is the case, as will be seen by the figure, in the antennae of the 

 larva oi Hydroiiliilus, where the partition between the two streams ends 

 just posterior to the distal end of the basal joint of each antenna. 



Verloren * "notes that, in the antennas of the larvee of Ephemera 

 diptera he had never been able to observe the circulation of the 

 nutrient fluid, except in the first joint, where the current enters on 

 the inner side and returns on the outer side. The direction and 

 extent of the currents of blood in the antennas are the same in the 

 larva of Ephemera diptera as in that of Hijdrophilus, but, as the 

 literature at the author's command fails to give the necessary data in 

 regard to the currents of blood in the antennae of other insects, and 

 he was not able to obtain specimens suitable for further observations, 

 it is unsafe to predict that the currents in the antenna of insects 

 generally follow a similar course. 



It will be seen by a glance at the figure that, with one excep- 

 tion, all the streams of blood have their outward course on the inner 

 side of each ajDpendage ; the exception is in the maxillae, where the 

 outward course of the blood is on the outer side. It would be 

 interesting to know if, in other insect larvae, the streams of blood 

 entered the maxillfe on the outer and returned on the inner side. 



As the circulation in the appendages of the head of the larvae of 

 Hydropliilus has no capillaries, the progress of the blood is so little 

 checked that one can count the pulsations of the heart as well in the 

 returning currents as in the outgoing ones. 



For the purpose of detailed study of the circulation of the blood 

 not only in the antennae and trophi but in all parts of the body, the 

 young larvfe of Hydrophilus ofler special advantages, on account of 

 their transparency, which is so great that their blood-corpuscles can 

 be readily seen imder the Microscope, without using extremely high 

 powers. The egg-cases of Hydrophilus can be collected in summer, 

 and the larvae easily reared in a small aquarium. If a suitable 

 aquarium be chosen, and placed beneath any kind of a fly-trap, in 

 such a way that the flies captured will fall, living, into the water, a 

 healthy brood of larvae of Hydrophilus can be fed with a minimum of 

 attention. 



/3. Myriopoda. 



Ventral Organ of Geophilus.t— The gland which emits a red 

 liquid by certain disks in the median ventral line of G. Gahriellis has 

 been studied by N. Passerini. The disks are epidermal structures about 

 • 2 mm. in diameter in adults, and are placed in slight depressions of 



* Verloren, M. C, 'Mc'moire en re'ponte a la question suivante: Eclaircir par 

 des observations nouvelles le phe'nomene de la circulation dans les insectes,' 1844. 

 t Bull. Soc. Entomol. Ital., xiv. (1S82) pp. 323-8. 



