Agassiz now began to feel an increased anxiety about his collections. During the six years of his stay in the United States he had explored the whole Atlantic sea-board as well as the lake and river system of the Eastern and Middle States, and had amassed such materials in natural history as already gave his collections, in certain departments at least, a marked importance. In the lower animals, and as illustrating the embryology of the marine invertebrates, they were especially valuable. It had long been a favorite idea with him to build up an embryological department in his prospective museum; the more so because such a provision on any large scale had never been included in the plan of the great zoological institutions, and he believed it would have a direct and powerful influence on the progress of modern science. The collections now in his possession included ample means for this kind of research, beside a fair representation of almost all classes of the animal kingdom. Packed together, however, in the narrowest quarters, they were hardly within his own reach, much less could they be made available for others. His own resources were strained to the utmost, merely to save these precious materials from destruction. It is true that in 1850 the sum of four hundred dollars, to be renewed annually, was allowed him by the University for their preservation, and a barrack-like wooden building on the college grounds, far preferable to the bath-house by the river, was provided for their storage. But the cost of keeping them was counted by thousands, not by hundreds, and the greater part of what Agassiz could make by his lectures outside of Cambridge was swallowed up in this way. It was, perhaps, the knowledge of this which induced certain friends, interested in him and in science, to subscribe twelve thousand dollars for the purchase of his collections, to be thus permanently secured to Cambridge. This gave him back, in part, the sum he had already spent upon them, and which he was more than ready to spend again in their maintenance and increase.