302 Royal Society. 



section of Terebratula australis, which I got from Prof. Carpenter, 

 showed that the minute canals referred to belong to a vegetable 

 parasite of the same kind as those of the Bivalves. 



6". Gasteropoda '. 



Nearly all examined Gasteropods, viz. Cerithium tuberculatum, 

 Aporrhais pes-Pelecani, Turbo rugosus, Murex brandaris, Murex 

 trunculus, Ilaliotis, Vermetus, Trochus, Littorina littorea, Terebra 

 myurus, Tritonium cretacevm, contained vegetable parasites in their 

 shells ; and in some these were as numerous as in the Bivalves, and 

 showed also sporangia. Besides these fungi, the shell of Trochus 

 also contained in its most superficial layers unicellular pyriform algae 

 with green contents. 



7. Annelids. 



Even in this group the unicellular parasites were found, viz. in 

 the calcareous tubes of two Serpulce from the Scotch coast. 



8. Cirrhipeds. 



The same parasites also occurred very numerously in the shells of a 

 large Balanus. On the other hand, the genera Diadema and Lepas 

 were free from them ; and with regard to the straight tubes of Polli- 

 cipes described by Quekett, which also occur in Tubicinella, I am 

 inclined to reckon them amongst the typical structures. 



9. Fishes. 



The scales of Beryx ornatus, from the clay, contain very numerous 

 and pretty parasitic structures, which almost exactly agree with those 

 figured by Rose in his fig. 5. They undoubtedly also belong to the 

 simplest form of fungi, but are of greater interest, inasmuch as they 

 are fossil and seem to constitute a new genus. I was not able to find 

 parasites in any other fish-scales, notwithstanding that I examined 

 scales of all living and many fossil species of Ganoids and many 

 Teleostei. 



These are the facts which I have been able to gather, up to this 

 time. I have no doubt that all will ageee with me in regarding this 

 question as one of great interest for the zoologist as well as for the 

 botanist. The former will now be obliged to study these parasitical 

 structures as thoroughly as possible, in order to decide which tubular 

 structures of the hard tissues of animals are typical and which are 

 not ; and for the botanist a new field of investigation is opened, which 

 not only draws attention by the somewhat strange forms offered for 

 investigation, but is also of great interest in a physiological point of 

 view. It seems to me probable that the parasites dissolve the car- 

 bonate of lime of the hard structures into which they penetrate, by 

 means of an exudation of carbonic acid, which secretion would seem 

 to take place only at the growing ends of the fungial tubes, as they 

 never lie in larger cavities, but are always closely surrounded by the 

 calcareous mass. In some cases, as in the horny fibres of sponges, 

 it seems probable that the parasites simply bore their canals by 



