Even this new accommodation soon became insufficient, and in the spring of 1882 a new morphological laboratory was commenced in accordance with plans suggested by himself. He was to have occupied them in the October term, 1883, but did not live to see them finished. As might have been expected from his own career, he regarded the mere teaching of what is known as a very small part of his duties as Lecturer; and as soon as any of his pupils became sufficiently advanced, he urged or rather led them to undertake original investigations; and he had the satisfaction before his death of seeing the researches of his pupils (such as those by Messrs. Bullar, Sedgwick, Mitzikuri, Haddon, Scott, Osborne, Caldwell, Heape, Weldon, Parker, Deighton and others) carried to a successful end. In each of these inquiries he himself took part, sometimes a large part, generally suggesting the problem to be solved, indicating the methods, and keeping a close watch over the whole progress of the study. Hence in many cases the published account bears his name as well as that of the pupil. In the year 1878 his _Monograph on Elasmobranch Fishes_ was published as a complete volume, and in the same year he received the honour of being elected a Fellow of the Royal Society, a distinction which now-a-days does not often fall to one so young. No sooner was the Monograph completed than in spite of the labours which his lectures entailed, he set himself to the great task of writing a complete treatise on _Comparative Embryology_. This not only laid upon him the heavy burden of gathering together the observations of others, enormous in number and continually increasing, scattered through many journals and books, and recorded in many different languages, as well as of putting them in orderly array, and of winnowing out the grain from the chaff (though his critical spirit found some relief in the latter task), but also caused him much labour, inasmuch as at almost every turn new problems suggested themselves, and demanded inquiry before he could bring his mind to writing about them. This desire to see his way straight before him, pursued him from page to page, and while it has resulted in giving the book an almost priceless value, made the writing of it a work of vast labour. Many of the ideas thus originated served as the bases of inquiries worked out by himself or his pupils, and published in the form of separate papers, but still more perhaps never appeared either in the book or elsewhere and were carried with him undeveloped and unrecorded to the grave. The preparation of this work occupied the best part of his time for the next three years, the first volume appearing in 1880, the second in 1881.