204 NATURAL SCIENCE. ^^: 



to fix itself so firmly and also to drop off at will, is interesting. The 

 anatomy oi Ixodes is not by any means a new subject; from Pagen- 

 stecher's almost monographic description, which formed vol. 2 of his 

 "Anatomic der Milben " in 1861, to Professor Batelli's " Comuni- 

 cazione preventiva " in the Monitove Zoologico Italiano for 1891, a good 

 deal has been written about it. I have used the word " rostrum " 

 hitherto for the anchoring organ because that is the name usually 

 given to it; but the appellation is scarcely a happy one, because 

 in other mites it is applied to the whole portion of the body in 

 which the mouth-organs are placed, whereas the anchoring apparatus 

 in Ixodes is only one of those organs. It is the homologue of what 

 is often called the labium in other Acari, but which is not in any 

 sense the same as the labium of insects ; it is a maxillary lip, 

 answering to the maxillae of insects or the pedipalps of other 

 Arachnida. It is a paired organ, or perhaps I should say paired 

 organs ; but the basal parts of the two sides are broad and flattened, 

 and are fused at their inner edges, so as to form a lower lip closing 

 the mouth and bearing the palpi ; the distal parts are rod-like 

 though free, flattened on their inner edges and lying close against 

 each other, but capable of some divarication. On the outer and 

 lower edges these rods are armed with a large number of strong 

 recurved hooks or spines. On the upper surface of this maxillary- 

 lip are two longitudinal channels in which the mandibles play back- 

 ward and forward. The latter are provided at their distal extremities 

 with elaborate cutting organs, and can be protruded a little beyond 

 the lip. They cut the hole into which the rod-like ends of the 

 lip are pushed ; the rods being then slightly divaricated, hold with 

 extreme tenacity ; but they also enlarge the hole a little, so that 

 when the creature brings them together again they can be with- 

 drawn, and it can return to its grass-lands and lay its eggs in 

 peace. Another point of interest discovered not long since by 

 Winkler is, that Ixodes possesses a heart, or dorsal vessel ; and as, 

 with the single exception of Gamasus, it is the only heart-like organ 

 known in the Acarina, while its one-chambered form is probably 

 about the simplest arrangement known in the Arthropoda, it is 

 worthy of special remark. 



Anyone keeping a large Ixodes alive will scarcely fail to be struck 

 by its frequent and wide changes of colour ; it is the Chameleon 

 among Mites. An instance of tliis is related in Sir J. Hooker's 

 " Himalayan Journal," which one would almost hesitate to quote 

 from a work of less authority. Ticks are very common on Lizards, 

 and Hooker found a black and yellow Lizard which had three Ticks 

 on it ; one was on a black part, and was black ; a second was on a 

 yellow part, and was yellow ; the third was just on the line dividing 

 the two colours, and one half of its body was black, while the other 



appeared yellow. 



Albert D. Michael. 



