. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 214 ARACHNIDA. Fig. 110. very important pecu- liarity, but which was in some measure in- dicated in the pre- ceding period. Its size is slightly di- minished anteriorly, and the vitellus con- sequently is divided e into two portions. The smaller and an- terior part (a) is rea- dily distinguishable from the dorsal part of the foetus, and occupies the place which sub- sequently becomes that of the corslet; M. Heroldt consequently terms it the thoracic re- gion. The other part is the abdominal region, which is very cons
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 214 ARACHNIDA. Fig. 110. very important pecu- liarity, but which was in some measure in- dicated in the pre- ceding period. Its size is slightly di- minished anteriorly, and the vitellus con- sequently is divided e into two portions. The smaller and an- terior part (a) is rea- dily distinguishable from the dorsal part of the foetus, and occupies the place which sub- sequently becomes that of the corslet; M. Heroldt consequently terms it the thoracic re- gion. The other part is the abdominal region, which is very conspicuous, occupies more than one-half the bulk of the ovum, and seems to constitute the greatest portion of the abdomen. If the inferior surface of the abdominal region be examined, there will be seen, in addition to a spot which ornaments that part, some addi- tional oblique and curved folds, which indicate the formation of the integuments; another and a more important change has now taken place on the middle line of the superior surface; viz. an obscure straight band (b) which commences at the thoracic-abdominal constriction, and reaches to the extremity of the ovum, becoming gradually narrower in that direction. This band, which does not give off lateral processes in any part of its course, is to be considered as the rudiment of the heart or dorsal vessel. The fluid which it doubtless contains in its interior is motionless. Heroldt thinks that the forma- tion of the fluid is anterior to that of the parietes in which it is enclosed : he also be- lieves that it is the albumen which gives origin to the circulatory apparatus, and further attri- butes to it the origin of all the integuments. These are, doubtless, important questions to solve, but as they are the result of speculation rather than direct observation, we have deemed it proper to omit the theories by which they are supported, and confine ourselves to a simple enunciation of the facts The eyes (d) are now distinguisha
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