Internal Anatomy of Uropoda Krameri. By A. D. Michael. 5 



triculus, and is quite straight and very thin and small in diameter ; it 

 has exceedingly delicate, semitransparent walls, without the conspicu- 

 ous circular bands of muscle so commonly found embracing the corre- 

 sponding part in the Oribatidae. The oesophagus proceeds upward 

 and backward from the mouth to the anterior edge of the ventriculus, 

 which it enters on the ventral aspect of that viscus, and a trifle behind 

 its anterior margin. There is a slight enlargement of the cesophagus 

 before entering the ventriculus, but not anything of the nature of a 

 proventriculus, or sucking stomach. During life, slow, regular, peri- 

 staltic movements may sometimes be seen passing along the oesophagus 

 in a backward direction. 



The ventriculus varies considerably in form ; it is a large organ 

 in comparison to the size of the creature, occupying nearly half the 

 length, and nearly two-thirds of the width of the body. It is com- 

 pressed dorso-ventrally. The principal mass is more or less trapeze- 

 shaped, the anterior margin is, however, always somewhat the wider, 

 and appears more so than it really is in consequence of the arrange- 

 ment of the caeca. The hind-margin is rounded (fig. 8), or pro- 

 longed in the central part (fig. 9), so as to extend somewhat 

 backward. The whole organ is much stronger and more muscular 

 than any other part of the canal. The caeca of the ventriculus, 

 particularly during life, are comparatively shallow, and widely open ; 

 often almost losing the character of caeca and becoming mere 

 lobes or pockets. They are arranged as follows, viz. there are 

 four principal lobes (cee), these proceed from the dorsal level, and are 

 rounded projections of the corners of the ventriculus, irregular in 

 form, and often having the outlines more or less divided into 

 secondary very shallow lobes, or wrinkles. Of these four lobes the 

 anterior pair project outward, while the posterior pair are directed 

 rather backward, and often have a tendency to curl inward. The 

 anterior margin of the ventriculus, between the front pair of larger 

 lobes, is almost wholly occupied by five smaller lobes ; the three 

 central of these are rounded and very shallow, and are indeed little 

 more than undulations ; they proceed from the dorsal part of the 

 anterior edge. The remaining pair are a Httle longer, although still 

 short, and are curious horn-like structures curving toward the median 

 hne and pointed (c«i) ; they arise from the ventral part of the 

 anterior edge. In addition to the eight above named there are 

 usually a pair of small, rounded, mamillary projections from the 

 ventral surface (fig. 9). 



In the large size of the ventriculus, and the shortness of the cseca 

 which proceed from it, the ordinary Gamasid type seems to me to be 

 departed from. In the genus Gamasus, &c., the ventriculus is often 

 a comparatively small and narrow organ, which appears as if its chief 

 office were to form a point of communication between its own 

 enormous caeca and the hind-gut. These cseca often extend quite 

 from the anterior to the posterior extremity of the body, and are 

 irregularly placed, intertwining with the Malpighian vessels to some 



