ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 443 



The conclusion drawn is that the condition of the birds as regards 

 fatness or thinness determines whether they shall moult or not. The 

 seasonal " pigmental changes in the blood," however, go on as usual, but 

 are not apparent when there are no new feathers to be coloured. In 

 the single tanager which was induced to moult in winter by a tempera- 

 ture change, the green potentiality was proved to exist. In the others, 

 which did not moult till spring, the scarlet tendency had succeeded the 

 green without the latter ever having found expression. " We have thus 

 proof that the outward manifestation of the sequence of plumage in these 

 birds is not in any way predestined through inheritance bringing about 

 an unchangeable succession, in the case of the tanager, of scarlet-green, 

 scarlet-green, year after year." 



Two additional points may be noted. The green winter plumage of 

 the male Scarlet Tanager is the permanent dress of the young of both 

 sexes and of the adult female, and is therefore presumably the ancestral 

 and more primitive hue. But in the allied Summer Tanager, Piranga 

 rubra (Linnaeus), the male remains scarlet throughout the year under 

 ordinary conditions. 



INVERTEBRATA. 



Mollusca. 



Phagocytic Organs of Molluscs.* — L. Cuenot has studied the 

 little-known phagocytic organs and cells of Molluscs. By injecting 

 Chinese ink or solid carmine he was able to demonstrate in many Molluscs 

 the existence of fixed phagocytes, grouped or scattered, either forming 

 autonomous organs, or situated within other highly vascularized organs. 

 These phagocytes have frequently a topographical relation to the arterial 

 vessels of the liver ; in Aplysians and terrestrial Pulmonates they invest 

 the extremities of the line arterioles externally, thus recalling in a 

 striking manner the phagocytic apparatus of decapod Crustaceans. In 

 Chiton it is the endothelium of the arterioles which has the phagocytic 

 power ; in other forms the hepatic arteries terminate in an absorbent 

 region, a kind of sponge (Mactra, Scaphander), while in others they 

 bear numerous spongy nodules (Cardium, Donax, Scroblcularia). In 

 many cases the phagocytes are within the blood-spaces of a renal organ, 

 such as the left kidney or papillary sac of the Diotocardia, the single 

 kidney of Monotocardia, the nephridial gland (Tenioglossida;), or the 

 appendix to the branchial heart of many Cephalopods. The phagocytes 

 are scattered throughout all the folds of the simple kidney of Tenio- 

 glossidre, while in the Stenoglossidse they are concentrated in the 

 accessory folds. This relation between the phagocytes and the renal 

 spaces recalls the analogous arrangement in certain fishes (Squatina, 

 Teleosteans). In two groups the fixed phagocytes are arranged in the 

 lacunae of the gills (most Monotocardia, Cephalopods). In Solen mar- 

 ginatus the small and very numerous phagocytic organs are situated 

 within the labial palps on the arterioles which supply these appendices. 



* Arch. Zoo]. Exper., liv. (1914) pp. 267-305 (4 pis ). 



