INSECTA 123 



and in which the sperms are received from the male and stored ; 

 also the colleterial glands, a pair of highly developed branched 

 glands opening separately just behind the aperture of the 

 spermathecae. The secretion of the colleterial glands forms 

 the capsule for the eggs. 



It is evident that in pairing the spermatic fluid is trans- 

 ferred by the male to the spermathecal pouches of the female, 

 and that, as in the crustacean, the act of fertilisation may take 

 place long after the event of pairing. The eggs are fertilised 

 when they are ripened and liberated. The sixteen eggs freed 

 from the sixteen tubes of the ovaries are held by the gonopo- 

 physes until the secretion of the colleterial glands has been 

 completed around them into an egg-case, ' cocoon/ or ootheca, 

 which contains the eggs and the spermatozoa. 



The development of the egg is somewhat complicated. A 

 general blastoderm is produced, the yolk not segmenting, and 

 the blastoderm surrounds the egg. The cells are flat dorsally, 

 but ventrally are columnar. The posterior cells, followed by 

 the anterior flattened cells, are produced into folds which 

 meet and fuse to form an amnion over the ventral thickened 

 part of the blastoderm. A long median groove is formed on 

 this ventral embryonic portion, and from this is derived the 

 endoderm and the mesoderm. The endoderm subsequently 

 encloses the yolk, the mesoderm is resolved into a series of 

 coelomic pouches, and an anterior stomodeal and a posterior 

 proctodeal invagination appear and deep en, to meet and fuse 

 with the enteron. The growth is accompanied by changes which 

 vary according to the group, and in some cases are profound ; 

 but in all the coelom becomes practically obliterated by the 

 overgrowth of the mesenchyme and the haemocoel, and persists 

 only in the formation of the gonadial tubes. The tracheae 

 are developed by ectodermal invagination, and the wings and 

 limbs as expansions of the body wall. 



The young cockroach at hatching is white in appearance, 

 but the eyes are black. It is in all respects like the adult 

 except in size and the absence of wings. Some five to 

 seven ecdyses are passed through, and at the last ecdysis it 

 is furnished with wings in the male or their rudiments in the 

 female. 



