i894. SOME SHELL-BORING ALG^E. 19 



The examination of the living plant is, as the French algologists 

 state, extremely troublesome and fragmentary. The most satisfactory 

 method of examination is by decalcification of the shell with Perenyi's 

 fluid. ^ This solution slowly dissolves the calcareous matter of the 

 shell, and fixes the protoplasm of the boring plant, without destroying 

 its colour. The three commonest and most readily recognised plants 

 are Gomontia polyrhiza, Hyella ccsspitosa, and Mastigocoleus testarum. 

 Gomontia produces distinct green patches, which, seen with a pocket 

 lens, appear as numerous branching green filaments radiating from a 

 common centre. At certain times dark green specks, the organs of 

 reproduction or sporangia, are observable on the filaments. These 

 sporangia, recognisable readily enough, when young, as part oi Gomontia, 

 acquire such peculiar characters ultimately, that there is every 

 justification for the mistake made by Lagerheim, who discovered 

 them, of describing them as independent plants of the genus 

 Codiolum. Hyella and Mastigocoleus are often found together, and 

 also intermixed with Gomontia. When found pure, Hyella is dis- 

 tinguished from Mastigocoleus by its patches, which are smaller, more 

 numerous, closer together, later confluent into a network which 

 may give the shell a mottled appearance " like a Fritillaria petal." 

 Both genera give patches of the same colour, grey, blue-black, or 

 violet (Payne's grey) ; but in Hyella one cannot make out with a 

 pocket lens such fine radiating filaments as compose the patches in 

 Mastigocoleus. The red alga, Conchocelis rosea, Bait., was not known 

 until 1892, when Batters (5) obtained it in 6 — 8 fathoms off the 

 Cumbrae Islands, in the shells of Mya truncaia and Solen vagina. 

 Conchocelis is recognisable to the naked eye as a pink stain 

 penetrating into the substance of the shell. Many of the genera, 

 and the two fungi especially, give no external indication to the naked 

 eye of their presence in the shell, and are only recognisable after 

 decalcification and subsequent microscopic examination. 



It would be out of place here to enter into a consideration of the 

 numerous interesting botanical questions discussed by Bornet and 

 Flahault. It must suffice to give an adapted form of their table 

 of genera, and the characters by which they are most easily 

 recognised. 



A. Coloured Plants : — 



I. Rhodophyceae (Red algae) 

 Bangiaceae ? 



Filaments branched, septate, chromatophores pink and star-shaped, spores (?) 

 single. — Conchocelis. 



1 Perenyi's fluid: iNitric acid, lo per cent., 4 vol. 



Alcohol, 3 vol. 



Chromic acid, 05 per cent., 3 vol. 



This reagent has long been known to zoologists. I used it through their 



suggestion in the Plymouth Laboratory in 1889, on calcareous algae. 



C 2 



