At Easter, 1867, Haeckel returned to Jena through Morocco, Madrid, and Paris. He spent a few of the pleasant spring weeks at the Strait of Gibraltar and in the South of Spain. In the fine bay of Algeciras (opposite to Gibraltar on the west) the current of the Strait brought swarms of interesting medusæ, siphonophores, and other “plancton-animals” into his net. In his solitary walks through the mountain forests of Andalusia, in the incomparable Moorish palaces and the cathedrals of Seville and Cordova, Granada and the Alhambra, he gazed on that wealth of Spain in treasures of Nature and Art which had excited his boyish imagination in the vivid pictures of Washington Irving. With his return home a crisis occurred in his career, from our biographical point of view, such as we find at one point or other in the lives of all great men. Up to the present the course of his life has advanced steadily onward, so that the simple chronological order afforded the most natural thread for our narrative. With this crisis his activity broadens out more. His ideas, almost all of which are presented in the _General Morphology_, form a great and continuous stem, which throws out a large or a small flower on one side or other, according to the stimulus received. His life crystallises about Jena; however many journeys he makes, he always feels that he will return to his centre at Jena. Nothing in his later career ever shook him from this ideal and personal base. In the summer after his return to Jena, 1867, he married Agnes Huschke, daughter of the distinguished Jena anatomist. He shares the happiness of this second marriage down to the present day. Of their three children, the son is now a gifted artist at Munich; the elder daughter is the wife of Professor Hans Meyer, proprietor of the Leipsic Bibliographical Institute, who is particularly known in science by his ascent of the Kilimandschars; the younger daughter is still at home with her parents.