ARACHNIDA ANIMAL PREPARATIONS. 135 



Books which may be consulted: W. Saville Kent's 'A 

 Manual of the Infusoria ' ; Griffiths and Henfrey's ' The 

 Micrographic Dictionary'; Pritchard's 'History of the 

 Infusoria.' 



ARACHNIDA. This class of animal life containing the 

 spiders may become very interesting and instructive objects. 

 It seems hardly necessary to say where they may be found, 

 or how to collect them ; but it may be necessary to enjoin 

 keeping them moist when they are required for permanent 

 objects or for dissection ; diluted glycerine or diluted acetic 

 acid will effect this. 



The respiratory system, the circulating system, the spin- 

 ning organs, and even the eggs, are very interesting, but a, 

 knowledge of dissection must be gained before the student 

 can make a successful study of this branch. 



The Arachnida are very plentifully distributed the mites 

 or Acarini, such as the Acarus domesticus (cheese mite) and 

 the Acarus farince (flour mite) are good objects for the 

 J-inch objectives used binocularly, either alive or when 

 mounted without pressure. 



Books which may be consulted: ' Micrographic Dictionary ' ; 

 Blackwall's ' British Spiders ' (Ray Society) ; Walker's 

 ' British Spiders ' (Ray Society). 



ANIMAL PREPARATIONS. The number of these objects 

 is legion ; and little else can be done here than to say that 

 animal preparations, as a rule, require special preparation 

 and treatment. Still there is the raw material to collect, 

 and this should be carefully preserved, in order that when 

 examined, its characters shall be faithfully delineated. 



The hairs of animals and scales of fish present no unusual 

 difficulties; but such subjects as skin, tongue, liver, lung, 

 &c., should be reserved until the student has become a 

 moderately expert experimentalist. Frogs, mice, rats, rab- 

 bits, and guinea-pigs are generally pressed into this service. 



