BY the death on March 3 of Prof. E. B. Wilson, the United States has lost her foremost zoologist. During his long tenure of the professorshipin Columbia University he made some outstanding discoveries in his science. He studied the growth and structure of the so-called ‘trochophore’ larva which is specially characteristic of the annelid worms. It is also found in the Mollusca, a group widely divergent in structure from the worms. Further, it occurs in the Polyzoa Entoprocta and Phorerudea, and ina modified form it is seen in the Nemertinea. There can be no doubt thatit represents in modified form the common ancestor from which all these groups diverged. If we put them all together, we see that in this way the origin of a large proportion of the Invertebrate is accounted for.