HALF- AX-HOUR AT THE MICROSCOPE. 139 



metamorphosed into my other little friends, the Hypopi. 



Mclntire saw the Hypopi, now probably blood-suckers, leave 

 their host's back (the Obisium), and wander over the floor and 

 sides of the cork-cells, and found that when they died, they drew 

 up the two hind pairs of limbs, so as to be scarcely visible, and 

 to give the appearance in mounted specimens of Acari with only 

 four legs. 



Now, it appears that Westwood in July, 1870, described two 

 species of Acari having apparently only the two anterior pairs of 

 limbs under the generic name oi Acarelhis. In December, 1872, 

 was published in the Monthly Micro. Jour7ial^ a paper by J. G. 

 Tatem, on two more species of the supposed new genus Aca?'ellus. 



Most mites in their early stage have, so far as known, only six 

 legs, acquiring another pair as they reach the mature condition. 

 There is no a priori reason why there should not be mites born 

 with only two pairs of limbs ; but Mclntire's observations seem to 

 render it very doubtful (to say the least) whether^ if there be any 

 such, they have as yet been found. Mclntire points out the diffi- 

 culty in giving credence to so great a change in the mouth-organS; 

 as that from the suctorial one of Hypopiis^ to the mandibulate (or 

 chelicerate at any rate) form in Gamasus, but with the surprising 

 transformations already known to science, it will not do to allow 

 too great weight to such an argument. A stronger one I believe to 

 be, that the young of Gamasi may be found in pedicellate ovisacs 

 on the Watchman beetle ; such I take to be the " Uropoda umbilica " 

 of Curtis ("Farm Insects," pp. 199, 398). The subject will be 

 found a most interesting one in its various bearings, and I can 

 only commend to our members the thoughtful perusal of the 

 various papers mentioned, which may help them to form conclu- 

 sions of their own on the subject, and, it may be, stimulate inde- 

 pendent research. 



Spider. — It is often a very difficult task to give the names to 

 mojinted specimens with certainty, and it is one from which 

 cautious men shrink through fear of committing themselves. The 

 one before me is, however, so characteristic, that I do not think 

 there is much risk in naming it a male example of " Tetragnatha 

 extejisa" which will be found described at length in Blackwall's 

 British Spiders (Ray Soc. Trans., Vol. II., p. 367, and figured 

 on PI. XXVIIL, Fig. 265. 



In examinmg a spider, the best plan is to pop it for a brief 

 period into gin ; then take it, and holding it on one of the old- 

 fashioned microscope forceps having a weak spring, by the two 

 hinder legs of the left side, examine first the eyes with a lens of 

 sufficient power, noting carefully their number, form, and arrange- 

 ment ; the form, etc., of the Cephalothorax. Then look to the 

 parts of the mouth, the falces, maxillae, lips, sternum ; gently 



