ENTOMOLOGY PYCNOGONIDES. 403 



jointed legs, and yet considers it as one of the Anuelidaus, denying it a place 

 with the Acari, aud designating it pTOvisionaUyEKtozoonfolKculorum. When 1 

 proposed (in the article by Simon) to designate the animalcule for the present 

 an Acarus, it was with the persuasion that as yet we know in it no more 

 than the first states of one of that class, an opinion which remains unshaken 

 in my mind. Even should the course of development described here be 

 proved in the main correct in one or other, or even in both of the modifica- 

 tions, it would rather confirm this idea, since the author has evidently made 

 assumptions without evidence, when he takes a mass of cells in the hind 

 part of the animalcule for an ovary, and imagines that the egg is formed out 

 of such cells apart from the parent. The complete development of this mite 

 remains, therefore, to be discovered by future researches. 



Koch (Wiegin. Arch. 1844, i, 217) has given a synoptic view of the 

 group of TICKS. He is disposed to separate them from the mites, as a 

 distinct order, on account of the differences in the reproductive organs, 

 corresponding to the peculiar mode of pairing, and in the respiratory organs, 

 which consist outwardly of a pair of spiracles placed at the sides of the 

 abdomen. He divides them into three families : 1. Argasida, the genera 

 Or/iitJiodoros (2 species) and Argas (5 species). 2. Ixodidte, the genera 

 Hyalomma (16 species), Htemalastor (1 species), Amblyomma (47 species), 

 Lrodes (32 species). 3. Rhipistomida, the genera Dermacentor (10 species), 

 Hcemaphysalis (4 species), RhipicepJial/ts (9 species), Rhipistoma (2 species). 



PYCNOGONIDES. 



Quatrefages (Compt. Rend, xix, 150) has investigated the in- 

 ternal structure of the Pycnogonides, with the object of demonstrating 

 in them Phlebeuterismus : so he denominates the vascular structure of 

 the alimentary canal, when it becomes branched and sends off its branches 

 towards the surface of the body, in the absence of organs of circulation and 

 respiration. The observations were made upon Nymphoti gracile, Amiiiothea, 

 new species, and Phoxichilus spinosus, Lch., and they agree perfectly with 

 those of Milne Edwards on Nyniphon fifteen years previously. The slender 

 gullet (oesophagus) is clothed with a glittering membrane [lined with vibra- 

 tory cilia] ; the stomach is wider and furnished with five blind pouches at 

 each side, wlu'ch penetrate into the legs, last of all a small intestine traverses 

 the abdomen, at the end of which the anus is placed. The brain consists of 

 a globular mass, which Lies above the gullet at its origin ; in Phoxicliilus the 

 eyes are in immediate contact with this, in Ammothea a short club-shaped 

 process of the brain enters the tubercle which bears the eyes. The spinal 

 chord consists of four ganglions which lie in close juxtaposition betwcrn 

 the intermediate legs. Not the least trace is there of organs for respiration 





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