ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 479 



The first division embraces the ectoderm and its derivatives. 

 Here would be placed in order the skin, nerves, glands, teeth, mem- 

 branes, bones, and organs of sense, and all other organs derived from 

 the outer germ-layer in as nearly as possible the order of their 

 appearance in the embryo. 



To the second division belong the endodermal structures, the 

 lining of the alimentary tract, the liver, respiratory organs of verte- 

 brates, endostyle of Tunicates and the thyroid and thymus glands, 

 pancreas, spleen, and stomach. 



The mesoblastic tissues may be divided into two great groups : 

 the first, those of the mesenchyma, embraces the spicules of sponges 

 and the skeleton of Echinoderms, smooth muscles, connective tissue, 

 fat-cells, blood, blood-vessels, heart, lymphatics ; and, lastly, cartilage 

 and bone. To the other division, to which the term mesothelial tissues 

 may be applied, belong the peritoneum of the vertebrates and its 

 homologues in other groups, striated muscle, and its modification, 

 electric organs, the segmental organs of the lower forms, and the 

 excretory organs of the higher forms, sexual organs, then the stomo- 

 deum and its glands, and the proctodeum and its appendages. 



The position of the mouth of vertebrates and its accessories is 

 uncertain, as doubts exist whether it is comparable to a portion of the 

 stomodeum of the lower forms or is a superadded feature. 



In the case of compound organs the preparations should be placed 

 with their most characteristic elements. Thus the liver should be 

 placed with the hypoblastic tissues, the nerves and skin with the 

 ectodermal, &c. In cases of series of sections of one animal, they of 

 course should be kept together. 



Dr. Dim mock adopts a different plan. Each of his slides is 

 numbered in the order of preparation, and then two card catalogues 

 are made, one by organs, the other systematic, each card referring by 

 a number to the corresponding slide. On these cards can be entered 

 full accounts of the specimen, its mode of preparation, the special 

 features presented, &c., and thus with a slight additional amount of 

 labour, the advantages of each system of arrangement may be 

 obtained. 



Blackham's Object-Boxes.* — Dr.G. E. Blackham takes the common 

 rack-boxes for twenty-four slides, and putting on the cover, pastes 

 a piece of stout twilled muslin on the back and lapping over on to 

 the cover. This forms a hinge, and gives the boxes a uniform look. 

 Each box is devoted to a special series or class of objects, and 

 properly labelled, and stands up on end in a revolving book-case. 

 The slides lie flat, and the whole collection is in reach from the 

 working table, without getting out of the chair. For indexing each 

 box Dr. Blackham, with an electric pen, makes a label covering the 

 inner side of the cover, the name of each slide is written on this, 

 on the line opposite the slide itself as it stands in the box. These 

 boxes are cheap, convenient and portable, and are, he considers, 

 preferable to the more elaborate and costly cabinets of drawers. 



* Proe. Amer. Soc. Micr., 6th Ann. Meeting, 1883, pp. 236-7. 



