ZOOLOGY AND BOTANY, MICEOSCOPYj ETC. 57 



In a scorpion — ButJius enropceus (?) — the structure of whicli has 

 already been investigated by Huxley, the author finds what Prof. 

 Huxley failed to see, the constrictor muscles by which the pharyngeal 

 sac is closed ; it will be remembered that Huxley ascribed the closure 

 of the sac to the elasticity of its walls. Vertical or oblique muscles 

 surround the organ and are inserted into its inferior border. At the 

 upper border they are inserted into the two lips of a groove, which 

 they cover like a bridge, and over which they are united. A section 

 of the pharynx taken perpendicularly to its long axis shows that the 

 organ has the form of a three-rayed star ; the dilatator muscles are 

 inserted between the ends of these rays, and the constrictors to their 

 ends. The oesophagus has a muscular investment formed by several 

 transverse bundles, but beyond it the heart is without any suctorial 

 apparatus. Numerous acinous glands, which open sej^arately on the 

 surface, are to be found in the maxillary portions of the ambulatory 

 legs ; they may be compared to the maxillary glands of spiders. 



The author confirms the accuracy of the account given by Plateau 

 of the digestive tube of the Phalangida ; the point of exit of the ducts 

 of their acinous gland has not been exactly determined, but they 

 probably open into the mouth. As it occupies the same position as 

 the maxillary gland of spiders, as discovered by Campbell, and the 

 poison gland found by Cronenberg in the Solpugidfe, the three sets 

 of organs may be regarded as homologous. 



The descriptions given by Plateau and Schimkewitsch of the 

 digestive tube of spiders are very exact, but MacLeod difiers from the 

 latter who thinks that all the muscles of the pharynx have a dilating 

 action ; he would rather ascribe a constricting function to those 

 lateral muscles which are inserted into the anterior angles of the 

 pharynx. 



The stomodaeum of the pseudoscorpions has considerable re- 

 semblance to that of scorpions and spiders ; the section of the 

 pharynx is four-rayed ; there is only a rudimentary sucking stomach. 



The various genera of the Acarina diifer from those of the groups 

 already considered by presenting very various arrangements among 

 themselves; several forms are separately described. 



The author concludes that the suctorial apparatus in all the 

 Arachnida which were examined is localized in the part of the 

 digestive tube which is in front of the oesophageal ring, with the 

 exception of the spiders in which there is a sucking stomach behind 

 the oesophageal ring, and in which the pharyngeal sac appears to be 

 undergoing degeneration ; and in the pseudoscorpions, where there 

 is a very rudimentary sucking stomach. In scorpions, spiders, and 

 pseudoscorpions the sucking apparatus is best developed at a definite 

 point in the stomodaeum; but in the Acarina and Phalangida the 

 whole or nearly the whole of that portion of the digestive tube 

 which is placed between the mouth and the nerve-ring plays the 

 part of a sucker, and is provided with a system of dilatator and 

 constrictor muscles which commences at a short distance from the 

 mouth. Organs analogous to the pseudo-trachese are found in 

 scorpions and Phalangida. 



