418 NOTES AND MEMORANDA. 



on these forms, wliich were made by Eedi (1728), C. C. Cuno (1734), 

 de Gecr (1783), and Hermann (1809) ; as at present regarded, there 

 are two (snbgeneric) sets of forms in the genus Analges ; in one 

 {Chelopii) the third pair of limbs are of great size, and provided with 

 a tubercular process to the second joint, which takes part in the 

 formation of a strong pincer ; in the second group {Pacliycnemici) 

 this tubercle is absent, although the appendages in question are of an 

 enormous size. Ilaller recognizes four species in the former, and 

 nine in the latter group ; but Megnin lool« upon three of these 

 latter, one of which is a new species (Gerthice), as all belonging to one 

 species, while the two new species of Haller (affinis and coleopteroides) 

 are regarded as belonging to the A. corvinus of Robin and Megnin. 



In his second paper Haller describes two new genera of avicolous 

 mites — Freyana (dedicated to Professor Frey) and Picohia ; the former 

 Megnin is inclined to regard as a sub-genus of Pterolichus ; the 

 second, which was found under the integument of Picus canus, appears 

 to be allied to Myobia, although it has, according to Megnin, 

 affinities to the parasitic Cliyletidije. 



Parasitic Chyletidse. — M. Megnin makes * some very interesting 

 remarks on parasitism, in which he founds a new division of these 

 forms ; as is well known. Van Benedon has pointed out the differences 

 between their habits of life, and has grouped them as (1) Commensal, 

 (2) Mutual, (3) Parasitic; on these there is no need to insist, but the 

 new class to which the name of auxiliary parasites is given must be 

 briefly described. The author one day chanced to enclose with some 

 Listrophora, which belong to the second group, two Chyletidce, which, 

 although of about the same size, are very much more active ; these 

 he observed to set on the Listrophora, to kill them, and suck their 

 juices. These, then, are truly auxiliary parasites ; truly so it should 

 be said, inasmuch as the African "beef-eaters" which extract the 

 larvae of the (Estrido} from the back of oxen, buffaloes, and gazelles, or 

 the falcons of South America, which perform a similar service for 

 the llamas, do not live solely on the parasites of these animals. 



A word is said as to the views of Van Beneden on parasites 

 proper. This author states that " the presence of several taeniae in the 

 human intestines constitxites ' un etat de sante enviable,' " but it is 

 pointed out that various Ungulata and even Carnivora can and do fall a 

 prey to these parasites ; and it is therefore proposed to divide the 

 forms into an inoffensive and a dangerous (pathogenic) group, 



A number of forms are described in detail and figured, and some 

 remarks made on their physiology, of which the following are the 

 more important points : — 



Differences in Form. — On a superficial view these are very striking, 

 but the differences exhibited are only to be observed in those struc- 

 tures which come into relation with the host. 



Digestive Apparatus. — The mouth is essentially a conical sucker, 

 formed by the fusion of the labrum and maxillas ; the enteric tube is 

 straight, and is but rarely provided with caeca; the anus is very 



* ' Jouin. Anat. et Phys.' (Robin), xiv. (1878) 416. 



