No attempt will be made to give a complete review of the literature relating to this group. Almost every systematic paper has something, because of the importance of the nervous system in classification and because in many cases the nervous system may be seen through the body-wall without dissection.

One of the first extensive accounts of these animals which also included quite a consideration of the nervous system was McIntosh in 1874. Several of the genus Nemestes were studied and the general form of the nervous system shown. Amphipheris is shown in a similar manner with a single lobe of the brain and with the two brain commissures. Tetrastemma is shown in a similar manner. Hubrecht in 1887 has an extensive paper in which the details of several nervous systems are shown as they show in reconstructions from sections. Eupolia girardi is especially well shown with its small dorsal and large ventral commissure and with three brain lobes. It is in this paper that Hubrecht makes his interesting comparison between the nemertians and cordates. In his paper of 1880 he has shown the structure and position of different parts of the nervous system of nemertians, especially of Cerebratulus of which he gives a very good figure. In this he shows a reconstruction of the brain with its chief nerves, ventral and dorsal commissures, general position of the cells, the two lobes of the brain on each side and the chief nerves. He also treats of nemertian nervous systems of many other forms, but not in so much detail.

Burger in 1890, '91, has extensive papers on the nervous system of the group. He discusses not only the general form, but also the minute structure of the nervous system of a number of different types. In 1895 Burger has another important paper on this group of animals. In it he shows in some forms a marked dorsal ganglion and a ventral ganglion with the typical nerves. Burger showed that all ganglion cells are unipolar, without membranes. Montgomery, 1897, discusses the minute anatomy of the nerve cells. Coe, 1895 and 1910, considers the general anatomy of the nervous system, but nerve details are for the most part not shown.

In a young Carinella cingulata Cole which I have studied by means of reconstructions, I find no unusual features. The nervous system is typical of the group. The brain, however, is not very clearly made up of two lobes on each side. This may be because the specimen used was a young one. This may also be the reason why the brain is not sharply marked off from the lateral nerve cords.

[Figure 1] shows the brain and part of the lateral cords from the ventral side. From the two halves of the brain come the nerves to forward parts. The small dorsal commissure is shown with its usual median extension. From the larger ventral commissure come the two nerves to the proboscis, lateral to these are the nerves to the intestine, while from the ridge of the lateral cords the lateral nerves are shown.

[Figure 2] in the larger drawing at the right shows the nervous system as viewed from the side with the dorsal side to the left. The central core of the ganglion and cord is to indicate the position of the fiber area. The small drawings at the left show various levels of the nervous system as seen in cross section. The ventral side is up. The drawing at the top is through the brain before the commissures are reached, the next lower is through the thickest part of the brain and the lower two drawings are through one of the lateral cords.

Burger, O.

1891

Beitrage zur kenntnis des Nervensystems der Wirbellosen. Neue Unter. über das Nervensystem der Nemertinen. Inst. a. d. Zool. Sta. Neah. 10.

Burger, O.