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the University of Cambridge, and began those researches on the 

 development of EJasmobranchs with which his name will be ever 

 associated. Before leaving Naples in the following summer he had 

 not only obtained some striking results as to the development of the 

 layers of the blastoderm, but had in reality solved the difficult 

 problem of the nature and origin of the urogenital system of 

 vertebrates. The work done in Naples showed talents of so high an 

 order that in the following October (1874) Balfour was on account of 

 it unhesitatingly elected a Fellow of his College. The following 

 winter he spent in a visit to South America with his friend Marl- 

 borough Pryor, but returning in the spring of 1875 resumed his 

 investigations at Naples. 



He had, at the meeting of the British Association at Belfast, in 

 August, 1874, made a brief statement of his researches, and in 

 October of the same year published a preliminary account in the 

 "Quarterly Journal of Microscopical Science." In the course of 

 1875 he contributed to the "Journal of Anatomy and Physiology" a 

 paper on the Urogenital Organs of Elasmobranchs, and laid before 

 the Royal Society an account of the development of the spinal nerves 

 in those animals, which was subsequently published in the " Philoso- 

 phical Transactions." He now commenced in the " Journal of 

 Anatomy and Physiology " a series of papers (the first of which was 

 published in January, 1876), giving a complete account of the deve- 

 lopment of the Elasmobranchs. These were afterwards (1878) 

 republished as a monograph. 



In the course of the summer of 1875, arrangements were made for 

 him to deliver at Cambridge a course of lectures on animal morpho- 

 logy. These he began in the following October, and soon after his 

 position was secured by his being appointed as lecturer to his College, 

 though his lectures as before continued to be delivered in the Univer- 

 sity buildings, and to be open to all students of the University. 

 Beginning with a very small audience, he rapidly drew students to 

 him by the powerful way in which he taught as well as by the 

 interest which he showed in the progress of each individual pupil. 



In spite of the time and energy taken up in organising and carrying 

 on these lectures, he himself always assisting in the accompanying 

 practical exercises, he pursued with unflagging ardour his original 

 investigations. No sooner had he finished the monograph on the 

 Elasmobranchs, than he set himself to write a complete treatise on 

 Comparative Embryology. The value of this work, the first volume 

 of which, treating of invertebrates, appeared in 1880, and the second, 

 of vertebrates, in 1881, cannot easily be exaggerated. It is not only 

 a masterly digest, in which the enormous number of observations made 

 during the last quarter of a century, and especially during the last 

 decennium, are marshalled in proper order, and their nature and 



