74 REPORT — 1844. 



animal has arrived at maturity, may be reproduced, yet the sexual organs are 

 always absent. (See experiments 3, 7, 13, 15.) Adult males of the species 

 Lycosa ohscura, Dysdera hombergii, and Philodromus dispar have been found 

 in a state of liberty with the palpi unequal in size and the smaller one en- 

 tirely destitute of the sexual organs. 



When the palpi of male spiders, which had been amputated before the 

 penultimate moult, are reproduced, the sexual organs, perfect in structure, are 

 reproduced also (see experiments 8,10,11,14'); unexceptionable evidence 

 in support of this singular fact is to be found in their reduced dimensions and 

 integrity of form, but it will scarcely be denied that the original germs of 

 those organs must have been removed with the detached palpi. That the 

 function of the sexual organs is not in the least affected by their reproduction 

 tiiere exists the most satisfactory proof. In the last of those experiments, 

 having for their object the determination of the seat of the sexual organs in 

 male spiders, recorded in this report, the male Tegenaria civilis, stated to have 

 possessed the right palpus only when introduced to the female, is identical 

 with that which was the subject of experiment 8 in the foregoing series ; 

 consequently, its sexual organs had been reproduced, yet the fertility of its 

 mate bore ample testimony to the unimpaired efhciency of their generative 

 agency. 



If experiments 6 and 16 be referred to, it will be seen that the stumps only 

 of mutilated parts are occasionally produced at the following moult, and that 

 the entire parts, of a small size, are sometimes restored at a subsequent 

 moult. 



Experiment 12 presents an extraordinary case of the stumps of the palpi 

 being produced at two consecutive moults after they had suffered mutilation, 

 though several legs of the same spider, mutilated at the same time, were re- 

 newed at the next moult after the infliction of the injury. 



The fact, that reproduced legs, immediately antecedent to the process of 

 moulting, are folded in the integument of the undetached portion of the 

 mutilated limbs, is clearly established by experiments 17 and 18. 



With some spiders the duration of life does not exceed the brief space of 

 twelve months, whereas it may be safely inferred from experiment 4 that 

 Segestria senoculata does not even complete its several changes of integument 

 and arrive at maturity in less than two years. The individual there stated 

 to have had the digital joint of the left palpus detached on the 18th of May 

 1839 was then about two-thirds grown, and must have been disengaged from 

 the egg in the summer of the preceding year, as this species breeds in the 

 months of May and June in North Wales. On the 28th of June 1840, the 

 third summer of its existence, it underwent its last moult and became adult. 

 Subsequent experiments made with both sexes of this spider tend to corro- 

 borate the accuracy of the above conclusion. 



Variations in the colour and size of spiders of the same kind, resulting from 

 differences in age, sex, food, climate, and other conditions of a less obvious 

 character, as they conduce largely to the introduction of fictitious species, have 

 long engaged the attention of arachnologists, while those arising from extra- 

 ordinary organic modifications, in consequence, perhaps, of their less frequent 

 occurrence, have been almost entirelyoverlooked. Tiie importance which cases 

 of the latter description possess in relation to physiology and systematic ar- 

 rangement will be best illustrated by a few examples. 



1. A supernumerary eye, situated between the two small ones constituting 

 the anterior intermediate pair, has been observed in an adult female Theridion 

 Jilipes. The total number of eyes possessed by this individual was nine and 

 their arrangement symmetrical. 



