1883.] Zoology. 553 



monary chamber, as well as in the body cavity. Here the em- 

 bryo undergoes a metamorphosis, becoming elliptical in shape. 

 It becomes a mere blood-sac, in which the next generation is pro- 

 duced. The germs increase in size and each becomes a redia, as 

 the nurse-form, provided with pharynx and intestine, is called. 

 When the redia is ready to come forth, it breaks through the 

 walls of the brood-sac (sporocyst), increases in size, finally be- 

 coming one-twentieth of an inch in length. Within them de- 

 velop from minute cells germs of which form Cercariae, each with 

 a sucker at the anterior end and another in the middle beneath. 

 They have, also, the anterior part of the body covered with ex- 

 ceedingly minute spines, and this form is believed by Thomas to 

 become the fluke-worm. Similar forms in the same species of 

 snails were at about the same time reared independently by Pro- 

 fessor Leuckart, in Germany, whose statements confirm those of 

 Mr. Thomas in the Zoologischer Anzeiger. Mr. Thomas' final 

 paper appears in the Quarterly Journal of Microscopical Science 

 for January, and is illustrated with several plates. 



* Chromatop hores in Crustaceans. — Dr. Max Weber has de- 

 scribed the structure of Haplophtkalmus and Trichoniscus, genera 

 belonging to the exceptional Isopod sub-family of Trichoniscidae. 

 The structure of Trichoniscus, save in regard to externals, had 

 not before been investigated. The copious details which such 

 an essay contains must necessarily be studied in the original. 

 Points of general interest, affecting other isopods, are duly in- 

 dicated. 



Dr. Weber makes a digression on the subject of chromatophores. 

 Leydig first showed that in the same situations as chromatophores 

 are found cells without pigment, but otherwise similar, the whole 

 forming one common system. Also animals of constant tint 

 possess non-contractile cells, presumably homologous with chro- 

 matophores. These are unquestionably distributed to the chro- 

 matophores. By means of gold chloride Dr. Weber has proved 

 this connection in the case of a common isopod (a young Philos- 

 cia). Anger, fear, love and other emotions undoubtedly cause 

 animals with chromatophores to change color ; yet it is usually 

 assumed that the play of the chromatophores serves to hide their 

 possessor, and perhaps in some cases for protection. But Leydig 

 saw tree-frogs amid their natural surroundings, change spon- 

 taneously their beautiful green for a dirty gray tint, just as they 

 are known to do in captivity, especially during murky weather. 

 The inference follows that a depressed temperature here acts on 

 the chromatophores, particularly when we consider that these or- 

 gans are an appanage of pcecilothermous animals. We learn 

 from v. Platen, Moleschott and Tubini, that light acting directly 

 on the skin (apart from what is termed the chromatic function, or 

 the indirect influence of light through the eyes) enhances the 

 metamorphosis of tissue. Dr. Weber concludes that one use at 



