408 General Notes. [ April, 
- For the geometric drawing of smaller objects the following 
` appliances are use 
1. One object-plate, which is placed below the glass plate and 
which, by means of an arm, may be moved up and down on one 
side of the cube. Upon this plate a small object imbedded in 
clay or any other suitable substance may be placed. 
2. A tubular diopter furnished with a lens. 
PRICES. 
A. Folding dioptrograph of polished mahogany for tourists $70 00 
B. Same as A, but not polished and without case . 55 00 
C. Same as A, but not folding (like the figure here given)........ 72 50 
D. Same as C, not polished 62 50 
The instrument is made by Luckhardt & Alten, in Cassel, 
Germany. 
Orauina:'—The life-history of this very interesting parasitic 
very ully nown, thanks to the investigations cited below. The 
subject is one of special interest to the teacher as well as to the in- 
vestigator, since it illustrates one of the simplest life-cycles known 
to us, and since the mode of development and oe rises 
5 ; somewhat higher than in typical unicellular Protozo 
iar tat—Hind-gut of batrachians (also found in planarians 
EF and, Na ideæ 
ae Period of reproduction. —FEarly spring, beginning as soon as the 
ae host leaves its winter quarters for the open water, and continuing 
only a few hee in some species, while lasting for two to three 
_ months in othe 
Mode of re pletion — Longitudinal and transverse fission. 
The adult polynucleated Opalina (O. caudata and O. similis have 
_ generally two nuclei, and occasionally only one) splits up by suc- 
cessive divisions into a large number of parts, each containing, 
- according to the species, one or more nuclei. These parts encyst 
< — while in the hind-gut of the host, and are then dropped with the 
_ fæces into the water. The spherical cysts (.025-.03™™) remain 
anged for several weeks on the bottom, and only begin their 
development after being swallowed by young tadpoles and pass- 
ing into the hind-gut. 
Material.—The adult Opalina may be easily obtained by cutting 
-out the hind-gut of a frog and pressing a little of the contents of 
1Th. W. Engelmann. Ueb on Infusorien. 
Morph. Ja nthe. Reming Entwickelung u. Fortpflanzung von 
: Zeller. Untersuchungen über die Fortpflanzung und die Entwickelung der 
si a ge Batrachiern schmarotzenden Opalinen. Zeitschr. f. wiss. - Zool., XXIX, Pr 
‘Wilh. Pfitzner. Zur Kenntnis der Kerntheilung bei den Protozoen, Morph. 
Jahrb., x1, H. 3, p. 454, 1885. 
` Moritz Nussbaum. Ueber die Theilbarkeit ge r lebendigen Materie. Arch. f. 
Mik. Anat., XXVI, pp. 487, 509 and 514, Jan., I 
E ee E Sai 
