ZOOLOaY AND BOTANY, MICEOSCOPY, ETC. 



143 



of the so-called apolar ganglion-cells of that organ appreciated. 

 Every life-process, in short, was visible through the transparent body 

 of the creature, so that if well studied by the help of this apparatus, 

 the student will have acquired a mental image or epitome of the 

 morphology and physiology of that great group of jointed animals, 

 the Articulates of the naturalist. 



Equally good results were got by its use in studying the embryo- 

 logy of the shad, where it revealed to the writer, and for the first 

 time to science, the presence of a so-called polar vesicle in the earliest 

 stages of development. 



In Fig. 26 we have a combination of the familiar animalcule 

 cage and the siphon slide, also designed by Mr. Holman. The edge 



Fig. 2G. 



of the cover or cap is bevelled, so that by rotating it against the 

 inflow and outflow tubes of the siphon arrangement, a very convenient 

 and effective compressor is obtained. The apparatus is equally as 

 valuable as the compressor before described, because of the certainty 

 with which one can gauge the amount of pressure which is applied ; 

 also on account of the facility with which water may be renewed in 

 it when used as a " moist chamber " for studying growing fungi, 

 without in the slightest degree disturbing these delicate plants. The 

 value of the apparatus is further enhanced by the facility with which 

 it may be used as a siphon-slide for keeping aquatic larvae, worms, 

 &c., alive for a lengthened period for study or exhibition. It is 

 equally useful as a dry compressor for holding, studying, and drawing 

 minute soft-bodied insects in the living state." 



Holman's " Life Slides."— Eigs. 27, 28, and 29 are three " life 

 slides," which were invented by Mr. Holman some years ago, 

 though we do not remember that they have been figured in this 

 country. 



(1) " Life Slide:'—Th.is slide (Fig. 27) consists of a 3 x 1 inch 

 glass slide, with a deep oval cavity in the middle to receive the material 

 for observation. A shallow oval is ground and polished around the 

 deep cavity, forming a bevel. From this bevel a fine cut extends, to 



