18 



EXPLANATION OF THE ENGRAVINGS. 



Plate I.— Fig. I, c. Chilodon cucullus, an Infusorial. Magnified about 

 650 diam. ; a, Nucleus with the Nucleolus ; d, the mouth-opening, sur- 

 rounded with a chitinous, fish-net-like apparatus, b, which is peculiar to 

 the whole family of the Nassulina , c, oily, globular bodies ; e, cilia, or 

 hair-like fringes ; ee, cuticula, cell-epidermis. 



Fig. I, cc. — d, nucleus with nucleolus; b, mouth; a, fish-net-like appa- 

 ratus ; c, oily bodies ; e, cilia. The Chilodon cucullus showing in division. 

 Magnif. about 600—700 diam. 



Fig. II. — Spirostomum ambiguum, an Infusorial, o, mouth ; c, cilia ; 

 /, lower end, turned up ; n. the chain-like nucleus with the nucleoli. Mag- 

 nif. about 550—600 diam. 



Fig. III. 8. — Daphnia pulex, a crustacean ( ? female), t, antennes ; c, the 

 brain ; e, the eye, movable by two muscular bands ; a, mouth ; I, the liver ; 

 g, the so-called " scale-gland ;" p, the rowing-legs ; q, two chitinous hair 

 appendages (setae) ; A, the heart ; b, the " summer-egg-bag ;" o, the eggs ; 

 i, the intestine ; m, muscles ; s, the two transparent scales ; an, the anus on 

 the abdominal end. Magnif. about 40 diam. 



Fig. IV. — The crustacean Cypris fasciata in its sixth state of develop- 

 ment. (The Cypris, according to Carl Claus, undergo nine changes in their 

 development), oc, the pigment-eye ; nc, nerve-centre ; ov, the position of 

 the ovarium ; L, the liver; st, the position of the stomach; Ch, the first 

 chitinous abdominal segment ; it, protoplasmatical cells in the shields 

 which are connected with the hair-like appendages by very fine ramifica- 

 tions ; g, the hind-leg under the " furca ;" /, the three-jointed fore-leg ; e, 

 the maxillary leg ; br, breathing apparatus (gill) ; m, muscles and liga- 

 ments ; max., the maxilla ; md., mandibula ; mdf. mandibulary leg ; 2 ant. 

 the antenne of the second pair ; all. and ah., the two connected shields ; 

 bas. 2, p. ant., the basal joint of the second antenne-pair ; 1, ant., the an- 

 tenne of the first pair; S. D., the so-called shield-gland. The figure is made after 

 C. Claus's work on the Ostracoda-developement, (Tab. II. fig. 17,) with 

 closer explanation of the internal organs. Magnif. 135 diam. Seen from 

 the right side. 



Plate II. — Fig. V shows the dorsal view of the Cyclops quadricornis, 

 a crustacean , a, the first, b, the second pair of the antennes ; c, the x like 

 pigment-eye on the forepart of the cephalothorax ; cth., the oesophagus : 



