FNTERNAL ANATOMY. 75 



tology of the fore-gut. Pagensteclier on the other 

 hand considered that he had found one in Arc/as 

 reflexus,* but Nalepa thinks that Pagensteclier must 

 have been mistaken. Berlese draws an intima as the 

 inner tunic of the oesophagus in the OribatidaB. The 

 inner tunic of the ventriculus consists of rather large 

 clearly nucleated cells, forming at first a tolerably even 

 layer; they are apt to remain so for a considerable period 

 in the anterior portion of the viscus ; when in this condi- 

 tion I have found these cells in Gli/ci/phagus platygaster 

 to measure from about 16 /x to about 30 /a in length 

 and width, by about 12 /UL to 16 p in thickness ; and to 

 be furnished with large and clear round nuclei of about 

 10 fj, to 13 ju in diameter by about 5 n in thickness. 

 Nalepa says that those of T. longior are as thick as 

 wide. A process takes place with these cells which is 

 not peculiar to the Tyroglyphidse amongst Acarina; 

 nor apparently to the Acarina amongst Arachnida,t 

 although, of course, there is considerable variation in 

 different orders, which it would be out of place to 

 enter into fully here, but which may be shortly summa- 

 rised as follows : The individual cells gradually elon- 

 gate inward into the lumen, not regularly or all together, 

 but irregularly in groups or single cells ; this elongation 

 continues until the cells present almost a columnar 

 appearance. Nalepa says that in Tyroglyphus longior 

 they are then 20 /u to 28 /* in length, with an extreme 

 width of 9 fi ; in many Acari, however, they are much 

 longer in proportion. The food which has been taken 

 into the ventriculus has been acted upon, partly prob- 

 ably by the secretion of the salivary glands, and partly 

 probably by the secretion of the glandular cells or 



* " Zur Anatomie von Argas reflexus" in ' Zeit. wiss. Zool.,' 1862, 

 Bd. xi, p. 145. 



f See Bernard, " Notes on some of the Digestive Processes in 

 Arachnida," ' J. B. Micro. Soc.,' London, Aug., 1893, vol. xiii, p. 427, 

 pi. vi. Berlese, " Ricercbe sugli organi e sulla funzione della diges- 

 tione negli Acari," ' Biv. di Patologia/ 1896, vol. v, p. 129. Reprinted, 

 Portici, 1896. " Circa il Mesointestino di alcuni Aracnidi," ibid., 

 1899, vol. vii, Nos. 58. Micbael, " Anatomy of Bdella," loc. cit., 

 p. 489. Henkin, op. cit., p. 571. 



