LINNEAN SOCIETY OF LONDOK. 4I 



year becoming a Fellow of the Eoyal College of Surgeons 

 there. Soon after lie became associated as Lecturer on Ana- 

 tomy with a brilliant circle — Edward Eorbes, John Groodsir, John 

 Hughes Bennett, and others — of whom Dr. W. B. Carpenter still 

 remains. Dr. Allen Thomson filled the Chair of Anatomy in 

 Marischal College, Aberdeen, from 1839 to 1841, when he passed 

 to occupy the Chair of Physiology in Edinburgh. Whilst occu- 

 pying this Chair he wrote the first part of a little work entitled 

 ' Outlines of Physiology.' This manual, had he completed it, 

 would doubtless have become extremely popular ; as far as it 

 went (pp. 308), it was considered by competent judges to be a 

 perfect model of its kind. At this time also, during Professor 

 Groodsir's temporary absence from ill-health, Thomson undertook 

 the duties of the Anatomy Chair, which he filled with the utmost 

 satisfaction to the students of the University. Six 3'ears after 

 he became Professor of Anatomy at G-lasgow ; and whilst engaged 

 in the arduous duties of that post he found time to write the 

 well-known and highly scholarly article entitled " Ovum " for 

 Dr. Todd's ' Cyclopaedia of Anatomy and Physiology.' So con- 

 scientious was Thomson, that he sought to verify facts relating 

 to many obscure and disputed points of animal embryology 

 whilst he was thus engaged. It thus happened that he spent 

 less than eight years over the production of that essay. Perhaps 

 the most valuable part of his contribution related to the ques- 

 tion of the mode of impregnation in Nematoid Parasites. Pie 

 supported generally the view of his distinguished pupil, Henry 

 Nelson, whose prize thesis at Edinburgh (afterwards published 

 in the ' Philosophical Transactions ') excited much controversy 

 abroad. In particular the views of Nelson were assailed by Pro- 

 fessor Bischofi", who declared that Nelson had mistaken epithelial 

 scales for spermatozoa ; but Thomson came to the rescue, and 

 showed that both himself and Meissner had confirmed the truth 

 of Nelson's statements in regard to the passage of spermatozoa 

 into the ovarian tube of Ascaris mysiax. Professor Thomson 

 was an accomplished linguist, and consequently he was able 

 to reply to his opponents eftectively in the pages of Siebold and 

 Kolliker's ' Zeitschrift,' as well as in the article above quoted 

 and elsewhere. He took excejjtion to the view of Meissner, 

 wlio believed in the existence of a micropyle in the unimpreg- 

 nated ovum of Ascaris mi/stax ; Thomson holding, with Nelson, 

 that there was no true vitelline membrane, and consequently no 

 micropyle, in the ovum of Ascaris at the time when the spermatic 

 corpuscles first arrived at the germs in order to penetrate them. 

 The controversy thus excited went on for many years ; and some 

 of the subsidiary questions then raised can hardly be said to be 

 solved at the present time. More of this controversy would 

 have been heard had not Henry Nelson taken his departnre for 

 Dunedin, New Zealand, where he died long before his eminent 

 friend and teacher left the Northern University. 



