Entomology : with special reference to its biological and economic aspects . Tansverse section of germ layers of Clytra. c, ccelom sac; n,neuroblasts (primitive nervous cells).—After Lecaillon. may share in the formation of the definite body-cavity, thoughthe last arises independently, from spaces that form betweenthe yolk and the mesodermal tissues. From the coelom sacsdevelop the muscles, fat-body, dorsal vessel, blood corpuscles,ovaries and testes; the external sexual organs, however, aswell as the vagina and ejaculatory duct, are ectodermal inorisin. DEVELOPMENT 155 Entoderm.—At its anteri
Entomology : with special reference to its biological and economic aspects . Tansverse section of germ layers of Clytra. c, ccelom sac; n,neuroblasts (primitive nervous cells).—After Lecaillon. may share in the formation of the definite body-cavity, thoughthe last arises independently, from spaces that form betweenthe yolk and the mesodermal tissues. From the coelom sacsdevelop the muscles, fat-body, dorsal vessel, blood corpuscles,ovaries and testes; the external sexual organs, however, aswell as the vagina and ejaculatory duct, are ectodermal inorisin. DEVELOPMENT 155 Entoderm.—At its anterior and posterior ends, the innerlayer jnst referred to gives rise to a mass of cells which are Fig. •?my Fig. 202. Transverse section of abdomen of Clytra embryo at an advanced stage of develop-ment, a, appendage; c, epithelium of mid intestine; g, ganglion; m, Malpighian tube;mi, muscular layer of mid intestine; ms, muscle elements; my, mesenchyme (sourceof fat-body); s, sexual organ; t, tracheal invagination.—After Lecaillon. destined to form the uicsciitcron, from which the mid intestine develops. One mass is adjacent to the blind end of the stomo- d?eal invagination and the other to that of the proctod?eal in-folding. The two masses become U-shaped (Fig. 202), and the lateral arms of the two elongate and join so that the entodermal masses become connected by two lateral strands of cells: by overgrowth and undergrowth from these lateral strands a tube is formed which is destined to Ijecome the stomach. and by the disappearance of the partitions that separate the mesenteron frc^m the stomodaeum at one end and from the proc- todccum at the other end. the continuity of the ali
Size: 1996px × 1252px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectentomology, bookyear1
