408 SUMMARY OF CURRENT RESEARCHES RELATING TO 



stalk of the brain, of which only ono is present. Tho norve of the 

 stemraata has both fine and strong fibres ; the former probably pass, as in 

 the Orthoptera, into the fork-shaped body, but tho latter go to the lander 

 part of the brain. Groups of cells send out processes into tho fan- 

 shaped body, and into tho " body of elliptical section." Other groups 

 in various parts of tho brain send out processes in various directions, 

 according to the position which they occupy. 



Machilis maritima.* — M. S. Jourdain has a preliminary note on this 

 Thysanurid, in which he limits himself to an account of the thoracic and 

 abdominal appendages, and of the curious exsertilo vesicles of this 

 animal. Externally to the coxa there is an articulated piece which tho 

 author compares with the exopodite of a crustacean appendage ; if this 

 view be correct, tho thoracic appendage of a Machilis may be said to bo 

 composed of a basal piece which carries an endopodite and an inarticulate 

 exopodite. The abdomen is formed of eleven, and not, as is generally 

 stated, of ten rings ; the first has no appendages ; the seven that succeed 

 carry a pair of delicate and short appendages, consisting of a very 

 reduced basal piece, and a longer joint which ends in a single unguis. 

 The appendages of the ninth ring are more developed, and these aro tho 

 organs which, by separating sharply, form the leaping organs. Those 

 of the tenth ring are modified with long, sebaceous, and multi-articulate 

 filaments ; while the last ring has one such appendage, which may bo 

 supposed to be formed by the fusion of two. The possession of these 

 abdominal limbs causes the author to regard Machilis as intermediate 

 between Insects and Myriopods. 



To get a good view of the exsertile vesicles which are found on the 

 inferior surface of the abdomen, it is necessary to place the animal in a 

 glass tube, the inner wall of which has been moistened ; it may then be 

 seen to suddenly protrude twenty-two vesicles, which have the form of 

 small oblong sacs, distended by liquid. These organs, which appear to 

 correspond to the abdominal vesicles of certain Podurids, are arranged 

 in two longitudinal rows on either side of the middle line. They 

 are formed by a portion of the integument of the abdomen, which 

 is delicate and membranous, is invaginated when in repose, and when 

 distended by the liquid of the general cavity is evaginated suddenly on 

 contact with a moistened surface. It is possible that they are organs 

 which absorb the water which is necessary to make up for that lost by 

 the animals when running over surfaces exposed to the rays of the sun. 



Brain of Phylloxera. f — M. V. Lemoine pursues his researches on 

 the nervous system of the winged Phylloxera punctata, and has made 

 sections of its brain. He describes the structure of the ocelli and their 

 innervation, the optic lobes, and the innervation of the compound eyes. 

 The author gives an intimate account of the various divisions of the 

 brain, the different commissures, the subcesophageal, and other ganglionic 

 masses. 



/3. Myriopoda. 



Brain of lulus. J — M. G. Saint-Eemy has examined the internal 

 structure of the brain of lulus sabulosus, and I. maritimus. The organ is 

 divisible into three ganglionic regions, the optic, the antennary or 



* Comptes Rendus, cvi. (1888) pp. 623-5. 



t Ibid., pp. 678-80. J Ibid, pp. 618-20. 



