. The crayfish : An introd. to the study of zoology. --. Crayfish; Zoology. 142 THE MORPHOLOGY OF THE COMMON CRAYFISH. scaphognathite lies, clearly indicates the natural boundary between the head and the thorax. It has further been observed that there are, in all, twenty pairs of ap- pendages, the six hindermost of which are attached to the abdomen. If the other fourteen pairs are carefully removed, it will be found that the six anterior belong to the head, and the eight posterior to the thorax. The abdominal region may now be studied in further detail. Each of its seven movable segments, exce
. The crayfish : An introd. to the study of zoology. --. Crayfish; Zoology. 142 THE MORPHOLOGY OF THE COMMON CRAYFISH. scaphognathite lies, clearly indicates the natural boundary between the head and the thorax. It has further been observed that there are, in all, twenty pairs of ap- pendages, the six hindermost of which are attached to the abdomen. If the other fourteen pairs are carefully removed, it will be found that the six anterior belong to the head, and the eight posterior to the thorax. The abdominal region may now be studied in further detail. Each of its seven movable segments, except the telson, represents a sort of morphological unit, the repe- tition of which makes up the whole fabric of the body. If the abdomen is divided transversely between the Fig. 36.—Astacnsfluviatilis.—A transverse section through the nine- teenth (fifth abdominal) somite (x 2). , extensor muscles ; /.«*., flexor muscles ; gn. 12, the fifth abdominal ganglion ; , hind-gut; ,, inferior abdominal artery ; , superior abdominal artery ; pi. XIX, pleura of the somite ; st, XIX, its sternum ; t. XIX, its tergum ; ep. XIX, its epimera ; 19, its appendages. s a. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Huxley, Thomas Henry, 1825-1895. London : K. Paul, Trench, Trubner
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1896
