MITES AND TICKS. 
O A *1 
‘■‘t / 
and oval in shape, and possesses four pairs of bud-like unjointed appendages, each 
tipped with two claws. The last pair of legs projects from the extreme hinder end 
of the body. The mouth is situated at the opposite extremity, but the only trace of 
jaws that it presents is a pair of stylets. There appear to be no organs of respira¬ 
tion or circulation; and, unlike what obtains in all true Arachnida, the sexes are 
united in each individual. The second group, Linguatulina or Pentastomida, is still 
less like the Arachnida. It includes internal parasites, which in form and mode of 
life present many points of resemblance to the intestinal worms. The body is long, 
broad in front, narrowed behind, and divided into a vast number of rings. Near 
the mouth there are two pairs of strong hooks, and although these are the only 
traces of appendages that the adult presents, the embryo is furnished in addition 
with two pairs of limbs, tipped with claws. It is mainly upon the evidence 
furnished by these limbs that the Linguatulina are regarded as degraded mites. 
One of the best known forms is Pentastomum tcenioides, which in the adult stage 
lives in the nasal passages of dogs and wolves. From these hosts the embryos 
escape to the outer world mixed up with the nasal mucus. Taken into the body 
along with the food of the hare or rabbit, they emerge from the egg, penetrate the 
walls of the intestine, and lodge themselves in the liver. Here they become 
encysted, grow, and go through a series of changes of form, accompanied by 
repeated ecdyses, until they pass into a state known as Pentastomum denti- 
culatum. If the flesh of the rodent containing P. denticulatum be devoured by 
a dog, the parasite passes into the skull of the dog, gradually takes on the form 
of P. tcenioides, and acquires sexual organs. Another species has been found 
living in the lungs of the Egyptian cobra, and a third in those of a species of boa. 
R. I. POCOCK. 
a spider’s sriNNERETS (greatly magnified). 
