Physiology of ILematopinus tenuirostris, Barm. 93 



able to trace the vessels which originate from the extremities 



of the strings of ova to their opening into the appendages of 



the tube. They originate at c in fig. 11, and, after a short 



course, open into one of the appendages (shown in situ in 

 fig. 13, d). 



Nervous System. 



Hcematop i nus tenuirostris has a cerebral ganglion and three 

 thoracic ganglia placed close behind one another. The large 

 cerebral ganglion is situated in the hinder part of the head ; 

 in the margin directed towards the forehead it has a small emar- 

 gination which divides it into two parts, right and left lateral 

 halves. The whole thus acquires the form of a bean. Its 

 length is 0*128, and its breadth 0190 millim. In front there 

 issue from it on each side to the antenna? two nerves in the 

 form of thin delicate threads. Their course has been already 

 particularly noticed (p. 85). Not far from these there starts 

 on each side a somewhat stouter but shorter nerve, which 

 is appropriated to the eye, the optic nerve. 



As regards the connexion of the cerebral ganglion with the 

 thoracic ganglia, I was able certainly to distinguish two 

 nerve-filaments at the hinder border of the former and the 

 anterior margin of the first thoracic ganglion ; but from their 

 delicacy and the solidity of the integument of the head and 

 thorax, I could not ascertain their further course and the mode 

 of their union ; and I see that in this respect I have fared no 



better than Landois. The supposition, however, seems to be 

 justified that these two nerves establish a connexion, like the 

 commissures in other insects. 



The three thoracic ganglia lie close together towards the 

 ventral surface ; and the first of them does not extend beyoud 

 the middle pair of limbs. The anterior one has a quadrangular 

 form with rounded anterior and posterior angles ; its greatest 

 breadth is in front, as is also the case with the other two gan- 

 glia of the thorax. In its anterior margin there is a faint 

 scarcely perceptible emargination. The second is more oval, 

 whilst the last decidedly acquires a quadrangular form. The 

 anterior thoracic ganglion is 0*124 millim. broad and 0*093 

 millim. long; the intermediate one 0*115 millim. broad and 

 0*091 long; and the posterior one 0*190 millim. broad and 

 0*128 millim. long. From the three ganglia of the thorax 

 there start on each side in front three nerves, one of which in 

 each case enters into a limb. I have been unable to trace the 

 course of the other two ; possibly, as Landois supposes^ one of 

 them is a sensitive nerve, while the other is appropriated to 

 the muscles of the body. The first two ganglia have only 



