362 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XVIII. 



you, it' you put some finely powdered carmine or indigo in the water 

 just behind the gills, you will soon see the coloured current pouring 

 out in front of the scaphognathite. 



The whole body of Palinurus is covered by an integument com- 

 posed of a number of epithelial cells which correspond to the 

 epidermis of man and higher animals. These cells secrete a substance 

 which forms a continuous layer all over the surface of the body and 

 limbs, and at the mouth and anus is continuous with the lining of the 

 gullet, stomach and most of the intestine. This layer is known as the 

 cuticle and throughout contains a substance known as chitin (Gr. 

 chiton, a coat). Here and there it is impregnated with salts of lime 

 to form the rigid armour-like portions of the exoskeleton. Any 

 hardened portion is known as a sclerite (Gr. skleros. hard). By 

 pouring a little strong acid on the hardened skeleton the lime will 

 be dissolved with the ebullition of gas bubbles. You must clearly 

 understand that the cuticle of the invertebrates is not homologous 

 with your own cuticle or that of other vertebrates, which is composed 

 of a number of flattened epithelial cells, that of the invertebrates 

 being non-cellular, i.e., only a secretion, and shows no nuclei or 

 cellular structure. 



Between each somite of the cephalo-thorax behind the mouth, 

 there is an infolding of the cuticle, each such infolding being called 

 an apod me (Gr. apodah, I partition), to form an internal skeleton, 

 or enduphragmal system, on the floor of the cavity. These sclerites 

 form in the middle line a tunnel or series of archways over the sternal 

 sinus, the nerve cord and sternal artery. Laterally they resemble the 

 bulkheads of a ship and give attachment to the muscles. 



The whole of this cuticular skeleton, including the apodemes and 

 the lining of the fore and hind guts, is shed or moulted periodically. 



The body is divided into two easily recognised regions, a posterior 

 abdomen made up of six somites (Gr. soma, body), freely movable 

 on one another in the vertical plane but having no lateral movement- 

 These somites are all clearly homologous with one another and 

 except the first each bears a pair of lateral appendages. Behind all 

 is a seventh segment, the " tail " or ttlson, which bears no append- 

 ages and is not a true somite. Anteriorly is the cep halo- thorax (Gr. 

 kephale, the head), covered dorsally and on the sides by a large rigid 

 shield or carapace, in which there is little indication of segmentation. 



