140 DESCRIPTIONS OF PREPARATIONS. 



by short filaments to a common ligament. This ligament is probably 

 attached, as in other Insecta, near the heart. The two oviducts open 

 beneath the last ganglion of the ventral chain into a short vagina. The 

 spermatheca consists of a short peduncle terminated by two slightly curled 

 vesicles. It opens into the vagina behind the last nerve ganglion. And 

 opening in turn behind it are the right and left colleterial glands, often, but 

 wrongly, termed sebaceous. They secrete the material which forms the 

 cocoon. 



The Cockroach, according to Cornelius, moults seven times before it 

 becomes adult. The first moult occurs immediately after hatching ; the 

 second a month later ; and the remaining moults at intervals of a year. The 

 adult stage is reached in the fifth year. The young animal differs from the 

 adult principally by inferiority of size, by the smaller number of facets in 

 the cornea of the eye, by the absence of wings, imperfection of the genitalia, 

 and in this family by lightness of colour, a feature, however, in which great 

 differences exist between adult individuals of this species. The absence of 

 a quiescent stage and of a period of abstention from food, such as exist in 

 Insecta with a perfect metamorphosis, is probably the reason why the fat 

 body persists, instead of being utilised as a storehouse of force during the 

 internal changes undergone by the organism. 



A Gregarine Clepsidrina blattarum is often found in the body cavity of 

 the Cockroach, and some remarkable Flagellate Protozoa in its intestine. 



The body is divisible, as in all adult Insecta, into a head, thorax, and ab- 

 domen. 



The head is broad transversely, and compressed antero-posteriorly. It is 

 carried vertically, not horizontally as in many forms. Its dorsal surface or Epi- 

 cranium is convex, and is marked by a Y-shaped epicranial suture, as in the Earwig. 

 This suture is in some specimens indistinct. The branches of the Y end in a 

 translucent spot of unknown function placed superiorly to the inner side of the 

 articulation of the antennae. The front of the head (= clypeus) is flat and broad, 

 and a labrum is moveably articulated to it, closing in the mouth anteriorly. The 

 antennae are long, filiform and many jointed. The joints are beset with hair (i.e. 

 are setose), and the basal joint is attached to a soft membrane, which closes the 

 socket. For the minute anatomy of antennae, see p. 145, infra. Behind the 

 antennae are the reniform compound eyes. There are no ocelli. 



The mouth is constructed for biting, and consists of three pairs of jaws : the 

 mandibles, the maxillae, and the labium. Each mandible is of one piece, tri- 

 angular, attached by two condyles to the head. Its inner edge has at the base a 

 grinding surface or mola, and in front of the mola and at the tip strong teeth. 

 Neither teeth nor mola are fashioned alike in the two mandibles. They appear to 

 interlock more or less perfectly. Each maxilla is composed of (i) a basal part, the 

 cardo y placed horizontally and articulating with the head ; (2) a stipes, which is 

 placed vertically, and bears (3) a five-jointed palpus on its outer edge articulated to 

 a basal piece representing the palpiger of some Insecta ; (4) a hood-shaped galea in 



