^316. 



THE AKACHNOIDAE. 



391 



The lower Arachnoidae produce only a small number of eggs at a time, 

 but these are often of a size disproportionately large to that of the 

 animal/''^ 



As yet, only very incomplete researches have been made on the elements 

 of the Sperm. It appears, however, that the spermatic particles differ 

 considerably in the various groups. Those of the Tardigrada have the 

 cercarian form ; those of the Scorpionidae, on the contrary, are simply 

 filamcntoid. But both kinds have very active movements which are 

 suspended by the contact of water. <" The Sperm of the Araneae always 

 contains spherical or reniform motionless corpuscles.^"* With the Aca- 

 rina, the spermatic particles are motionless and of most varied forms. ''^' 



by Wittick (Observ. quaed. de Aranearum ex ovo 

 evolut. Dissert. Halis, 1845, fig. 1, A.).* 



4 With the Tardigrada, the eggs are very large, 

 as are also those of Oribates, Sarcoptes and De- 

 tnodex. 



'•> See Doyire, loc. cit. p. 354, PI. XVI. fig. 5 

 (Macrobiotns), and Kolli/cer, Schweiz. Deukschr. 

 VIII. loc. cit. p. 25, Taf. II. fig. 16 (Scorpio euro- 

 paeiis). I have observed that the characteristic 

 movements of the spermatic jjarticles ceased in- 

 stantly from contact with water, and that the par- 

 ticles themselves became twisted and doubled. 



<) With Tegenaria, Sa/ticim, Lycosa and The- 

 ridion, the spermatic particles have the form of 

 round cells, while those of Micryphantes and 

 Clubiona are reniform or semilunar. They are 

 formed in groups in the mother-cells. With Tege- 

 naria, a round nucleus is easily distinguished in the 

 spermatic particles. With Lycosa, this nucleus is 

 oblong, curved and attached to the wall of the cell; 

 and this led me at first to think these cells were 

 the spermatic particles in their first stages of de- 



velopment, and that theu- definite form would be cer 

 carian. But I quickly abandoned this idea when I 

 found the same form in the seminal receptacle of 

 the females, where, evidently, the spermatic parti- 

 cles cannot be present except in their perfect state. 

 ? With Trombidium, Zetes, Oribates, and 

 Hoplophora, the spermatic particles are developed, 

 as I have satisfied myself, under the from of very 

 small, rigid corpuscles, in very large cells. With 

 Bdella, they are produced in a similar manner, but 

 are fusiform. With other Acarina they are found 

 of remarkable forms. Thus, in the testicles of the 

 Hydrachnea and Gamasea, I have observed round 

 masses of cuneiform bodies, at the larger extremity 

 of which tliere was an oblong granular spot. I 

 have also satisfied myself that these m.otionless 

 spermatic particles of such large size are preceded 

 in their development by round nucleated cells. In 

 the testicles of Ixodes ricinus, I have seen count- 

 less transparent staff-like bodies, i)retty long and 

 large, motionless, but swollen at one of their ex- 

 tremities when placed in water.! 



* [ § 316, note 3.] The development and struc- 

 ture of the eggs of Araneae have recently been 

 carefully studied by fVittick (Die Enstehung des 

 AracUnideneies im Eierstocke, die ersten Vor- 

 giinge in demselben nach selnem Verlassen des Mut- 

 terkiirpers ; in MiiUer''s Arch. 1849, p. 113), and 

 by J. f. Cams (Ueber die Entwickelung des Spin- 

 iieseies, in Siebold and Kolliker''s Zeitsch. II. 

 1850, p. 97). The structure of the ovary of these 

 animals is no less beautiful than singular ; it re- 

 sembles a bunch of grapes enclosed in a common 

 capsule. The eggs are develoijcd, each, on the ex- 

 tremity of a pedicle which is attached to the main 

 stem or rachis. The details of the development of 

 the ova are briefly as follows : Ou the extrem- 

 ity of the pedicle appears a delicate vesicle, or cell, 

 which contains a nucleated cell. This nucleated 

 cell is the germinative vesicle, with its dot, and 

 does not increase so rapidly in size as the vesicle 

 in which it is contained ; but this last dilates and 

 expands, and minute cells appear in the liquid, 

 lying between its membrane and the germinative 

 vesicle. These newly-formed cells constitute the 

 vitellus ; and when the ovum is completely formed, 

 it consists of vitellus in which is concealed the 

 germinative vesicle with its dot. In a word, the 

 <ivum is here formed as elsewhere, except that it is 

 developed on the extremity of a pedicle. In regard 

 to the peculiar bodies mentioned above by Siebold, 

 as found in tJie vitellus, their presence and struc- 



ture have been observed by both fFiCticli and 

 Cams ; they are composed of concentric layers 

 around a nucleus. Of their nature and function 

 nothing is known. — Ed. 



t [ § 316, note V.] I have studied the develop- 

 ment and nattu'e of the spermatic particles of the 

 Araneae and Acarina, but with results different 

 from those above mentioned. With the first of 

 these, they are developed, as usual, in special 

 daughter-cells, and invariably consist of an arcuate 

 staff, to which is attached a short but very, very 

 delicate tail ; indeed, ttiis tail is so tenuous that 

 only the best and highest microscopic powers can 

 bring it out. It escaped the watchful eyes of JVag- 

 ner and Leuckart, and led them to adopt errone- 

 ous views of the formation of these bodies (see 

 Art. Semen, Cyclop. Anat. & Phys. fig. 374). 

 With the Acarina, the particles have the same 

 form and character, but are much more minute anil 

 diSicult of examination. It would api)ear from the 

 description given above by Siebold, that he must 

 have taken for spermatic particles the peculiar 

 granule-like bodies found in the jpcrm of the 

 Araneae. These bodies are very hydroscopic, but 

 are homogeneous, and although I could make out 

 nothing further as to their structure, yet it is evi- 

 dent that they are wholly different from the true 

 spermatic particles, and cannot be considered as 

 either undeveloped or modified forms of these last. 

 — En. 



