410 Mr. A. H. H assail on the genus Lepralia, 



they are thrown upon the shore, or by rough and careless 

 handling; the damage which the Lepralia; sustain from these 

 several causes is however nearly the same in all, and consists 

 in the removal of the spines with which the apertures of most 

 species are furnished. I consider that it is in the first way 

 that Lepralia punctata, L. linearis and L. auriculata are in- 

 jured, for of these you may remove with the utmost care 

 very many living specimens from their bases, and yet not 

 find one perfect, that is, having the cells armed with spines ; 

 when these do occur, they are always met with on those cells 

 which are sheltered by some indentation of the surface upon 

 which they have developed themselves, thus clearly indicating 

 that they pertain equally to all the cells, but have been re- 

 moved by violence. Sometimes the spines are so abraded 

 that no trace of fracture can be detected ; this is the case 

 with the three species just named; in others, however, 

 especially the following, a portion of such spines usually re- 

 mains behind, as in Lepralia appensa, L. ovalis, L. immersa 

 and L. insignis. 



It cannot be doubted also but that the spines are frequently 

 either removed or obscured by a natural cause, viz. the deve- 

 lopment of an operculum, when they will still be found how- 

 ever on the marginal cells : this is frequently the case with 

 Lepralia auriculata. 



It may be asked whether an occasional development of 

 spines ever takes place in species usually destitute of these 

 appendages— it is my firm belief that such never occurs : the 

 number of species not provided with spines is but small ; I am 

 acquainted with but two species possessing calcareous poly- 

 pidoms whose apertures are not armed with spines, Lepralia 

 coccinea and L. pediostoma, and on these the search for spines, 

 I am convinced, would be a fruitless one. Lepralia variolosa is 

 figured in Dr. Johnston's c British Zoophytes ' without spines, 

 with which I have a strong suspicion that it will ultimately 

 be found to be furnished. 



Reviewing therefore the foregoing remarks, it will, I think, 

 be manifest that the effects of the operation of the first three 

 causes, locality, age, and the drying of the specimens, are not 

 material, whether acting singly or in combination on the same 

 species, nor such as are likely to lead to error in the definition 

 of species', not so, however, with regard to the fourth cause, 

 the mutilation of the specimens from violence; unless great care 

 be employed to procure perfect specimens, there is reason to 

 fear that injured and imperfect examples of a species will be 

 mistaken for a distinct species. The form of the apertures I 

 consider to be one of the best characters by which to recog- 



