THE BRYOZOA — BASSLER. 347 



tion of the fossil forms particularly, is based upon the zooecial 

 structure. 



On account of the compound calcareous colonies which many of 

 the bryozoa build, thin sections are a necessity in the study of some 

 of the orders, particularly the Trepostomata and Cryptostomata or 

 fossil stony bryozoa. Again the zoaria of many of the Cyclostomata 

 are so similar to those of the Trepostomata that thin sections are here 

 again required, while even in the Cheilostomata they are frequently 

 needed. The preparation of thin sections is described in a subse- 

 quent paragraph. 



In the Cheilostomata the form of the chitinous appendages such 

 as the operculum and the mandible of the avicularium is an essential 

 feature, and hence the preparation of these structures for examination 

 under the microscope as well as other preparations as described on 

 p. 371, are necessary in detailed study. 



JaveUe water. — The various zooecial structures in the recent bryozoa 

 are sometimes obscured by the ectocyst, the chitinous membrane 

 covering the zoarium and by remains of the animal tissue. These are 

 removed by boiling in JaveUe water, 7 whereupon the specimen as- 

 sumes the aspect of the fossil forms in which naturally all of the 

 chitinous and fleshy parts of the organism have disappeared. 



Ammonium-chloride process. — The zoaria of many recent bryozoa 

 are so semitransparent or glasslike that the various zooecial struc- 

 tures can be observed only with difficulty. However, they may be 

 brought out in great perfection and clearness by whitening the sur- 

 face with ammonium chloride. A simple apparatus for this pur- 

 pose is illustrated in figure 2. By blowing through the mouthpiece, 

 M, the fumes of hydrochloric acid (HC1) and ammonia (NH^OH) 

 will unite at the outlets of the tubes, O, and form a white sublimate 

 of ammonium chloride upon any object held at this point. This 

 sublimate can be deposited upon the object in such a uniform, thin 

 film, varying in color according to its thickness, from a light blue to 

 an ivory white, that all the details of structure are reproduced per- 

 fectly and can be viewed under the microscope without exhibiting 

 any crystalline structure of the ammonium chloride. By this process 

 the minute sculpturing or structures scarcely visible on the corneous 

 or transparent calcareous colony are brought out in clear relief. 

 While this whitening process is a great aid in the preliminary study 

 it is almost indispensable in the illustration of recent bryozoa by 

 photography. Fossil bryozoa also lend themselves admirably to this 

 process of study and illustration. It may be remarked that the am- 



7 Javelle water can usually be obtained from any druggist, but it is easily prepared by 

 dissolving 1 pound of washing soda in 1 quart of cold water and adding to this one-quarter 

 pound of ordinary bleaching powder (calcium hypochlorite). After filtering, the solution 

 should be kept in a tightly closed bottle. 



