430 TRANSFORMATIONS OF INSECTS. 



In 1824 Heroldt described the changes which occur in the 

 eggs of the spider (pulmoniferous) before it was hatched, and 

 his investigations are a wonderful piece of intelHgent and patient 

 research. He divides the growth of the spider within the &^^ — 

 from its first appearance as a shapeless and structureless germ 

 to the perfect condition when hatching took place — into eleven 

 stages, but there is not a strict line of division between the stages, 

 only different organs are formed, and various appearances are 

 presented gradually. 



Up to the period which Heroldt terms the seventh, the body 

 of the spider looks like an opaque structureless mass, but when 

 this commences, traces of rings, four in number on either side, 

 may be noticed. These are the rudiments of the legs. They 

 occupy the side of the front part of the Q.g^, and they are extended 

 downwards also. The end of the first leg is close to that of the 

 opposite side ; but the three others, though of greater length, 

 are separated by a space which is filled with a cloudy and some- 

 what transparent matter. This space is subsequently occupied 

 by the trunk and much of the abdomen. The future head is in front, 

 but is not yet rounded like in the perfect spider, but is flattened 

 forwards, and there is a ring on its sides which forms the palpi 

 of the jaws, and portions of the mandibles may be distinguished 

 in a very rudimentary condition. It is probable that all the parts 

 which appertain to the head, as the eyes, the hooks or the 

 mandibles, and the maxillae or jaws, have their limits well defined 

 at this period. In the preceding period, or the sixth, only the 

 general outlines of the head and body could be distinguished. 

 With respect to the head, it is nearly separated from the chest 

 (as in insects), and this fact is of importance, since in all the 

 full-grown spiders the confluence of the head and chest is most 

 intimate, and their original separation only indicated by a groove 

 of greater or less depth. 



The integument or skin of the foetal spider begins to be seen 

 at this time, and can be detected in the form of furrows or arched 

 folds. 



During the eighth period the feet, mandibles, and the head 

 become more definite as structures, and the whole ovum 

 diminishes in size in front, and is somewhat constricted so as to 



