McCracken, Egg-laying Apparatus of Silkworm. 263 



Bethe^ ('97) gives a review of the work of these investigators 

 and, in a series of careful experiments upon several species of 

 insects and other Arthropoda, discredits some of the previous 

 assumptions, notably those of Faivre, verifies many of the facts 

 and establishes certain theories. His experiments point to the 

 following conclusions: That the brain besides being the central 

 ending of certain peripheral nerves (nerves to the antennae-, eyes, 

 etc.) is an inhibitory center and exercises a tonus upon the muscu- 

 lature; that the influence of each half of the brain and sub-cesoph- 

 ageal ganglion is felt mainly in the extremities of the same side. 

 He showed that the decapitated insect in several species is still in 

 a condition to perform all of its characteristic movements, except 

 that there is a certain awkwardness and feebleness in these activi- 

 ties. Bethe also adduced evidence (in Hydrophilus and Astacus) 

 showing the independence of the thoracic ganglia. 



The present work deals with the behavior of the egg-laying 

 apparatus of the silkworm (Bombyx mori) in the normal, decapi- 

 tated and dethoraxed insect. 



It was not a matter of surprise to find the reproductive system 

 in the silkworm functioning through the ganglion with which it is 

 intimately connected. It was, however, of much interest to observe 

 the accurate response in every part of the system throughout a long 

 period of time after severance of head or head and thorax, the con- 

 ditions under which this response took place and the coordinate 

 movements in other parts of the body. 



the reproductive system. 



In the female silkworm, the paired ovaries consist each of four 

 elongated tubes, the ovariole tubes (Fig. i , O.t.), havingan expanded 

 length of about 36 mm. The terminal filaments of these ovarioles 

 or egg chains are united by a common filament to the dorsal 

 wall of the abdomen. These series of four ovarioles unite in a 

 short common oviduct about 2 mm. in length (Fig. i, Od.). 

 The two oviducts unite in a common vagina, an elongated chamber 

 with a length of about 6 mm. The vagina passes as a single tube 

 to the extremity of the body, where it culminates at the surface in 

 an ovipositor consisting of a short muscular tube terminated by 



^ Bethe, A., 1897. Vergleichende Untersuchungen iiher die Functionen des Centralnervensystem 

 der Arthropoden. PfiJger's Archiv der Physiologic, Bd. 68, pp. 449-544. 



