234 



In conclusion, he stated that although these suppositions might not 

 adequately explain all the phenomena that might be observed, still 

 this stmcture proves that there have been alternations of ligneous tis- 

 sue, either having tensions in different directions, or a self-existing 

 double refraction of different characters ; but he considers the sup- 

 position that the effects are due to tension agrees with the neutral 

 action of some parts and the general properties of others much the 

 best; and he felt convinced that the study of the double refraction of 

 the tissues of plants would be of great utility in arriving at a correct 

 knowledge of the manner of their development. 



Another paper, ' On the Minute Structure on a Species of Fanga- 

 sina,' by W. C. Williamson, Esq., was also read. 



In former communications to the Society, the author pointed out 

 the existence of a curious system of tubes and canals, penetrating the 

 parietes and septa of several species of foraminiferous shells, in which 

 the structure of Polystomella, some species of Nonionina and Am- 

 phistegina were described. On making sections of a species of Fan- 

 gasina, U'Orb., from Manilla, the existence of a much larger and more 

 interesting arrangement of tubes was discovered. The shell is con- 

 structed on the inequilateral plan of Truncatulina tuberculata, and 

 viewed as an opaque object, exhibits a series of vertical translucent 

 spaces, with the intervening parietes to which the foramina are limited. 

 Along each of the vertical septal lines there exists an irregular double 

 row of very distinct pits or depressions ; similar pits are also seen 

 inferiorly in the radiating septa which divide the different segments 

 of each convolution. On making a series of sections of the shell, we 

 learn that these pits or depressions are the external orifices of a cu- 

 rious system of intraseptal canals and spaces ramifying in its interior. 

 A section taken close to the inferior flat surface of the shells exhibits 

 a spiral translucent septum, separating the convolutions ; the seg- 

 ments present the ordinary foraminated aspect, and are arranged in 

 the usual spiral manner ; in the radiating interseptal lines are seen 

 numerous small orifices, which open, by means of short canals, into 

 the interseptal spaces immediately above them. On making a second 

 section, parallel to the first, but a little above the peripheral margin, 

 we perceive that there exists a number of large branching intraseptal 

 tubes and passages, which commence at the innermost segments and 

 proceed in a radiating manner towards the periphery ; these appear 

 designed primarily to multiply the number of external orifices ; but 

 in addition to this, they subsequently facilitate the establishment of a 

 free communication between the internal intraseptal spaces and those 



