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 Cercariz, 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 Zodlogischer Anzeiger. Mr. Thomas’ final 
r appears in the Quarterly Fournal of Microscopical Science 
for January, and is illustrated with several plates. 
CHROMATOPHORES IN CRUSTACEANS.—Dr. Max Weber has de- 
scribed the structure of Haplophthalmus and Trichoniscus, genera 
belonging to the exceptional Isopod sub-family of Trichoniscide. 
€ structure of Trichoniscus, save in regard to externals, had 
not before been investigated. The copious details which such 
an y contains must necessarily be studied in the original. 
riria general interest, affecting other isopods, are duly in- 
icated. 
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 
ming 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- 
i). 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 
‘aw tree-frogs amid their natural surroundings, change spon- 
taneously their beautiful green for a dirty gray tint, just as they 
ote 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- 
"S are an appanage of pcecilothermous animals. e learn 
V. Platen, Moleschott and Tubini, that light acting directly 
ae au 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 
