192 Mr. W. Clark on the British Trochus Cutlerianus. 



five lateral or peripherical cells — in all, eleven cells or more. The 

 germs formed of seven or eight cells only were most numerous. 



All my efforts to discover plants more advanced in their deve- 

 lopment remained without eifect. Those of which I have just 

 spoken all perished without growing any larger. I have, unfor- 

 tunately, been able to visit the locality of my Lycopodium inun- 

 datiim only in autumn and early spring, and I have never found 

 the least trace of spores in germination. 



Imperfect as my observations are, the germinative power of 

 the spores of Lycopodium is now demonstrated ; only we are not 

 yet able to say with certainty how the prothalliurn completes its 

 growth. 



According to what is known of the initial development of the 

 prothalliurn of the Ferns and the Equisetacese, this organ has 

 a very different mode of increase in the Lycopodiese. On the 

 other hand, it would seem to imitate very manifestly the primi- 

 tive form of the archegonium of the Ferns, — so much so, indeed, 

 that at first sight it might readily be taken for an imperfect 

 archegonium supported on a single basilar cell. 



If it is admitted that the bodies which I have observed are the 

 product (as seems very probable, from their resemblance to each 

 other) of a normal vegetation, the question arises, whether we 

 are to regard each of them as a vViA.\mt\\idiY\ prothaUium, ana- 

 logous perhaps in form and structure to that of the Ophioglossese 

 (the earliest development of which is still unknown), and de- 

 stined subsequently to bear sexual organs, or rather as a young 

 archegonium with a single basilar cell, which must be fecundated 

 doubtless ulteriorly by spermatozoids issuing, like those of the 

 Hydropteridese, from special spores resembling only externally 

 those from which the archegonia are produced. Of the two 

 analogies, the second seems to me, in truth, the least probable; 

 but there are so many relations of organization between the true 

 Lycopodiese and Selaginella, that it deserves to be taken into 

 consideration, and perhaps may ultimately prove to be correct. 

 These first positive results, which I am now enabled to make 

 kno^^^l, show sufficiently that an attentive and long-continued 

 study of the subject cannot be made in vain. 



XXIII. — On the British Trochus Cutlerianus {Clark), being the 

 ? Skenea Cutleriana of the ' British MoUusca ;' and on the 

 Trochus exilis of PhiUppi {Moll. Sicil ). By Wm. Claek, Esq. 

 To the Editors of the Annals of Natural History. 



Gentlemen, 7 Norfolk Crescent, Bath, February 1859. 



Mr. Jeffreys, in his " Gleanings,^^ which have lately appeared 



in the 'Annals,^ has impugned my discovery of the Trochus 



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