1888.] MICROSCOPICAL JOURNAL. 151 



forms. One fish, Gastrostomus^ discovered has no paired fins and lives 

 imbedded in mud up to its neck. The distance from the tip of its nose to 

 the articulation of the jaw is a third larger than from the joint to the begin- 

 ning of the tail, the body pi'oper, and opens like a huge funnel, while the 

 eyes are reduced to a pair of minute spots at the extreme point of the upper 

 jaw. Many of the hermit crabs, hard pi'essed for protection for their delicate 

 abdomens, are strangely modified. One Xylopagurus bores a hole in a 

 piece of wood or finds a hollow plant stem open at both ends and closes the 

 opening by his tail and stout anterior claws. The hermit, unlike most 

 familiar ones, is straight and not spirally coiled. Space does not permit an 

 enumeration of the odd and grotesque forms which people the ocean's bot- 

 tom, but anyone who can do so would find a visit to this museum of wonders 

 full of interest, perhaps novelty. The account is mainly a review of the 

 peculiarities of shape and color with not much which is of a speculative nat- 

 ure. The problems of the relationships between these divergent deep-sea 

 animals and their relatives whom we know better, and the search for the par- 

 ticular causes which have made particular forms what they are, are not entered 

 upon in these volumes, which attempt rather a picture of the facts than 

 monographic completeness. 



Yariatioiis in microscopic measurements. 



By CHAS. FASOLDT, Sr., 



ALBANY, N. Y. 



Having found that the measurements of the committee bf the American 

 Society of Microscopists and mine did not agree, I have attempted to discover 

 what the cause of the variation might be, and this is the result : — 



During the last six months I have worked considerably on investigations 

 into this matter, and to convince myself that the difference was caused by 

 the various applications of illuminations, etc., as given in the table below. 



The image of j*y-inch was the object on which these measurements were 

 made, and was ruled on a glass disc of No. 2 covering glass ^ J|y^j-inch in 

 thickness. All measurements were taken on the same ruling, with the same 

 microscope, objective, and eye-piece, under the same focus, and having the 

 microscope in the same position continually, and only changing the mirror 

 and excluding the one light while the other was used. A number of com- 

 parisons were made at each position and in the same temperature. 



A vSpencer objective was used for these measurements, but Bausch & 

 Lomb and Gundlach objectives were also tried, giving the same results. 



The microscope used is one constructed on my late patents and has a mi- 

 crometer for measuring similar to a cobweb micrometer. But instead of 

 cobwebs, three movable steel pointers are used, which are worked as fine as 

 this metal will permit. The stage is mechanical, and the main slide is moved 

 with great precision by a fine screw 100 threads per inch. 



Table shozving the variafiotis in measurements due to the different applications 

 op light and illuminatiofi. 



UNMOUNTED. 

 Lilies downward. Lamp light. Lines ufituard. 



Concave Mirror, - - !*„- in. xuffSuo — I Concave Mirror, - - -^^ in. icrofffo 



Plane Mirror, - - fV) '"• tooooit + I Plane Mirror, 



111. through objective, - -j% in. jffoVcrir ~r I m- through objective, 



MOUNTED ON GLASS. 



Lavip light. Day light. 



■1 i n 15 



To "'• TOOOffU 



Concave Mirror, - - -^ij 



Plane Mirror, - - y\ in. -fjrU^xf + 



111. through objective, - ^*u in. ywtiW + 

 July 3, iS88. 



Concave Mirror, 

 Plane Mirror, 



3.11 _ _L 



80 _L 



