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form consortial relations, it also becomes evident that the attempt 
which has been made independently by Dr. Brandt and myself, at 
generic and specific definition of the yellow cells, pending more 
complete investigation of the forms they may assume when culti- 
vated in the free state, is doubtless premature, and I think it pre- 
ferable to withhold for the present the diagnoses of species, 
prepared as a note at p. 383. It may suffice to say that, as Professor 
De Bary has suggested to me, the “ yellow cells ” may have some 
affinity to WoronhTs* Cliromo'phyton Rosanoffii , which they at any 
rate resemble in colour. 
D. Mr. George Murray f has pointed out the interesting analogy 
which exists between the young gonophores of Velella , which start 
in life provided with a stock of algsc, — u to the liymenial-gonidia of 
such lichens as Dermatocarpon , Polyblastici, &c., as described by 
Stahl. The hymenial-gonidia, which are the offspring of the 
thallus-gonidia, are carried up in the formation of the apothecia, 
and are cast out along with the spores. Falling in the same 
neighbourhood, the spores, on germinating, enclose with their fila- 
ments the hymenial-gonidia, which ultimately become the thallus- 
gonidia of the new lichen. The fact that among the animals the 
most closely allied to each other morphologically differ thus widely 
physiologically bears comparison with the near relations of the 
fungal parts of the lichens with the other ascomycetous fungi.” 
E. Professor Perceval Wright, in a letter J commenting on the 
subject of consortism or symbiosis, announces that he has observed 
that the spores of Chlorochytrium , and other algae, frequently also 
enter the bodies of animals. He also suggested in 1877 the possible 
relation of such cases to the lichen-gonidia question. 
A few years ago I was greatly perplexed by observing the 
zoospores of TJlva not being eaten, but vigorously burrowing their 
way into the bodies of the large and almost quiescent A r moebce 
which abounded in the same aquarium. Ho doubt this was a case 
of the same kind as those observed by Dr. Entz and Dr. Perceval 
Wright. 
F. M. Max Cornu § has called attention to the fact that not 
* Bot. Zeitung , 1880. 
f The Academy , No. 508 (1882), p. 67; and Jour. Boy. Micr. Sci., April 
1882, p. 245. 
X Nature , 16tli February 1882. § Comptes rendus , Dec. 1881, No. 26. 
