PULMONARY. 283 



Lifter ^ays that Spiders dart their threads in the same way that the 

 Porcupine darts his quills, with this difference, however, that in the 

 latter, according to the popular belief, the spines are detached from 

 the body, whereas in the former, these threads, though propelled to 

 a considerable distance, always remain connected with it. The pos- 

 sibility of this has been denied. Be it as it may, we have seen 

 threads issuing from the mammillae of several Thomisi from straight 

 lines, and, when the animals moved circularly, producing moveable 

 radii. A second use to which this silk is applied by the female Ara- 

 neides is in the construction of the sacs destined to contain their 

 eggs. The texture and form of these sacs are variously modified, 

 according to the habits of the race. They are usually spheroidal ; 

 some of them resemble a cap or tymbal, others are placed on a 

 pedicle, and some are claviform. They are sometimes partially en- 

 veloped with foreign bodies, such as earth, leaves, &c. ; a finer 

 material, or sort of tow or down, frequently surrounds the eggs in 

 their interior, where they are free or agglutinated and more or less 

 numerous. As they are voracious animals, the males, in order to 

 avoid a surprise and to prevent themselves from falling victims to 

 their premature desires, approach their females in the nuptial season 

 with the greatest circumspection and mistrust. They cautiously and 

 repeatedly touch them, and frequently for a long time before they 

 yield to their wishes, and when this is the case they quickly and 

 repeatedly apply the extremity of their palpi to the inferior surface 

 of the abdomen, protruding at each time, and as if by a spring, the 

 fecundating organ contained in the button formed by the last joint of 

 those palpi, and insinuate it into a sub-abdominal slit, near the base 

 and between the respiratory orifices ; after a moment's interval the 

 same act is repeatedly performed. Such is the mode of copulation of 

 a small number of species belonging to the Orbitelae. It is impos- 

 sible to avoid feeling the most lively interest in reading what has 

 been written upon this subject by that learned naturalist, who of all 

 others has most profoundly studied these animals, the celebrated 

 Walckenaer, member of the Acad. des Inscriptions et Belles-lettres. 

 The apparatus of the male organs of generation, or at least of what 

 are considered as such, is usually highly complicated and very various ; 

 it consists of scaly pieces, more or less hooked and irregular, and of a 

 white fleshy body, on which sanguineous looking vessels are some- 

 times perceptible, which is considered as the fecundating organ, pro- 

 perly so called ; but in the Arachnides with four pulmonary sacs, and 

 in some belonging to the division where there are but two, the last 

 joint of the palpi of the males only exhibits a single horny piece in 



