Royal Society. 225 



spine will primarily lie in a line with the first cleft of the yelk, 

 though it may afterwards deviate somewhat from that line during 

 the growth of the embryo. 



Lastly, it has been sought to discover what influence the artificial 

 application of the spermatozoon to only one side of the eg^ would 

 have upon the direction of the primary cleft of the yelk. The result 

 of this inquiry seems, very curiously, to be, that the first cleft of the 

 yelk will lie, under the circumstances stated, in a line with the 

 point of the g^^ that has been touched with the impregnating fluid. 



** Contributions to the Anatomy of the Brachiopoda." By Thomas 

 H. Huxley, F.R.S. 



In the course of the dissection of certain Brachiopoda with which 

 I have recently been engaged, I have met with so many peculiarities 

 which are unnoticed in the extant and received accounts of their 

 anatomy, that although the pressure of other duties prevents me from 

 attempting to work out the subject with any degree of completeness 

 for the present, I yet gladly avail myselC of the opportunity of com- 

 municating a few of the more important results at which I have 

 arrived, in the hope that they may find a place in the Proceedings of 

 the Royal Society. 



My investigations were principally made upon Rhynchonella psit- 

 tacea, for specimens of which I am indebted to Prof. Edward Forbes, 

 while Dr. Gray obligingly enabled me to compare them with Wald- 

 heimia flavescens and with Lingnla. 



1 . The Alimentary Canal ofTerehratulida. — Professor Owen, in both 

 his earlier and his later memoirs on the anatomy of the Terebratulidae, 

 describes at length the manner in which the intestine, as he states, 

 terminates on the right side between the lobes of the mantle. 



On the other hand, Mr. Hancock has declared himself unable to 

 observe at this point any such anal aperture, and concludes from his 

 own oliservations that the latter is situated on the ventral surface of 

 the animal in the middle line, just behind the insertion of the great 

 adductor muscle. M. Gratiolet, in a late communication to the 

 Academic des Sciences, takes the same view. To get rid of the ob- 

 vious difficulty, that this spot is covered by the shell, and therefore 

 that if the anus existed here, there would be no road of escape for 

 the fseces, Mr. Hancock and Mr. Woodward appear to be inclined 

 to suppose that some cloacal aperture must exist in the neighbour- 

 hood of the pedicle. 



The existence of any such aperture, however, has recently been 

 denied with great justice by Professor Owen. 



The result of my own repeated examinations of Rhynchonella psit- 

 tacea and of Waldheimia flavescens is — 1. that the intestine does not 

 terminate on the right side of the mantle as Professor Owen describes 

 it, but in the middle line, as Mr. Hancock describes it in Waldheimia^ 

 while in Rhynchonella it inclines, after curving upwards, to the left 

 side; and 2. that there is no anus at all, the intestine terminating 

 in a rounded csecal extremity, which is straight and conical in Wald- 

 heimia, curved to the left side and enlarged in Rhynchonella. 



I confess that this result, so exceptional in its character, caused 

 Phil Mag. S. 4. Vol. 8. No. 51. Sept. 1854. Q 



