936 RECORD OP CURRENT RESEARCHES RELATING TO 



pressed, so that, on superficial examination, there appears to be 

 only one fused ganglionic mass, while, in the latter, the thoracic 

 ganglia, at any rate, are separated from one another by extended 

 longitudinal commissures. Is this difference due to a new formation, 

 or to the elongation, as it were, of the separate parts of the cord ? 

 The result will show that his observations lead the author to be 

 strongly inclined to adopt the latter view. 



The cerebral ganglion of the larva is placed at about the middle of 

 the head, and directly on the cesophagus; it consists of two lobes, 

 pyriform in shape, and with their thickest ends approximated and 

 directed anteriorly. There is some difference in the form of the 

 masses in the younger and older larvte. From the anterior surface 

 there are given off four nerves for the mouth ; at about the same 

 place there arises the nervus recurrens, and behind these there is 

 an unpaired nerve which goes to the oesophagus ; shortly before this 

 reaches the midgut it enlarges into a ganglion; very similar rela- 

 tions are, so far as this is concerned, seen in the adult, save only that 

 the ganglia frontalia have considerably increased in size. The 

 ganglia of the paired bucco-gastric nerves are similarly larger, and 

 the double character which they had in the larva is exchanged for 

 an apparent unity. On the other hand, the transverse commissure 

 which connects these ganglia is much shorter than in the larva ; the 

 various intermediate stages between the two are to be made out in 

 successive stages of the pupa. The same is exactly true of the com- 

 missures of the oesophageal ring. With regard to the ventral chain, 

 the author is in agreement with Cuvier ; in the larva it ends, so far 

 as he has seen, at the point of separation of the second and third 

 segments of the body. In a larva 2 cm. long it measured • 2 cm. and 

 •07 cm. broad; in one 3*4 cm. long, it was -31 cm. long and '075 

 broad ; in the adult stage it measured • 79 cm., while the length 

 of the ganglia amounted to -52 cm., a length which had been 

 observed in some of the oldest of the larvae ; the agreement between 

 the two is sufficiently striking, and it only remains to note that the 

 breadth was in the adult somewhat greater, being in the proportion 

 of eleven to nine in the larva. 



The author enters into a detailed description of the nervous 

 system, an account of which would be altogether unintelligible unless 

 it were accompanied by the figures with which he illustrates it. 



Tlie second portion of the paper deals with the relations of the 

 tracheal to the nervous system ; and the third with an account of 

 the more minute structure of the ventral cord. In the larva there are 

 two investing layers, which are distinguished as the outer and the 

 granulo-cellular neurilemma ; the former is an obscurely striated 

 membrane, with elongated nuclei embedded in it. The latter forms a 

 stratum of finely granular substance, with clear rounded nuclei; 

 there are no definite boundaries to its cells ; it is feebly developed on 

 the dorsal, and well developed on the ventral surface of the cord ; 

 it is the part which, in connection with the tracheae, produces the 

 segmentation of the ventral cord. The ganglion cells surround the 

 central fibrous layer in an almost continuous investment, save at the 



