164 KEPOBT— 1880. 



is connected with that in another by means of disks in the zooecial walls,' 

 which have been called rosette-plates. 



These rosette- plates I found, as regards position, form, &c., furnish 

 characters which in some genera are of great use in the specific determi- 

 nation, and from what I have seen anticipate that in some cases they also 

 can be used to distinguish genera. By the position of the rosette-plates 

 in recent and fossil species (when the state of fossilization allows exami- 

 nation), the part of the zooarium from which fresh growth takes place is 

 in most cases clearly indicated ; and it seemed to me of great importance 

 that a comparative study of the endosarc and its position, and of the 

 rosette-plates, should be made ; and the arrangements of the Zoological 

 Station furnish every opportunity for so doing, and made it the more 

 disappointing to relinquish the investigation. 



ZooiotryoH pellucidus, the ctenostomatous species examined by Rei- 

 chert, being transparent, is very favourable for examination, and from 

 watching it in different circumstances I conclude that in the normal con- 

 dition the endosarc always consists of a large number of fine threads, 

 and when it is found as a more solid cord it is in a less vigorous state, 

 absorption of some of the tissues has commenced, and, if I am justified 

 in drawing conclusions from incompleted work, this condition must be 

 looked upon as pathological, or, perhaps, it must be considered the result 

 of a check to growth caused by periodical or exceptional causes, such as 

 the unsatisfactory nature of life in an aquarium. This was shown in 

 several cases in specimens which, when freshly collected, showed a vast 

 number of anastomosing threads, but after living some days in the 

 aquarium presented the thick cord in much the condition figured by 

 Reichert. 



After some considerable trouble I induced DiacJwris magellanica, a 

 transparent cheilostomatous species, to root upon some slips of glass, 

 placed in my small tank for the purpose ; but being successful in this only 

 just before leaving, I was unable to make the continuous observations 

 intended. It, however, seemed that while this species, which is brought 

 from a depth of 30 to 40 fathoms, would live in the aquarium, showing 

 for some time activity of the avicularia, and occasionally movement 

 of the polypide, and also throwing out radicles, there was, with this 

 exception, no further growth ; so that a bud, which was growing when 

 brought in, would remain at the same stage, and the contents of the cell, 

 which were of a cellular character, would separate into an irregular 

 network. 



From these and other observations, I saw reason to believe that besides 

 the study of actively growing specimens, much could be learnt from an 

 examination of the reversed changes, which take place when growth is 

 arrested ; and apparen.tly ari'est of growth takes place in some parts 

 frequently and perhaps in the whole periodically, when the endosarc will 

 become consolidated, and is thus a store ready for fresh growth. 



From the immediate neighbourhood, I found but few species not 

 mentioned in the paper published two years ago, but hope shortly to 

 draw up a list of additions from a somewhat wider range ; some are 

 species known in distant localities, thus again showing that the geo- 

 graphical range is often very large with the Bryozoa. 



' The rosette-plates may be seen also in the diaphragms of some Ctenostomata ; 

 in the avicularian chambers, and in Jldmbranijwra ccn-icornis is well developed at 

 the base of the projecting process. 



