308 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



hsematoxylin was used almost exclusively. For surface views the 

 specimens were studied unstained, or mounted in a mixture of glycerine 

 and acetic acid strongly tinged with methyl green. 



Up to the present time no comparative study of the eyes of the 

 different species of salpa has been made. Perhaps this is not strange, 

 for the group salpidae is so highly specialized that a knowledge of the 

 eye of this group is not likely to throw much light upon the relation 

 between the visual organs of the chordata in general. A very casual 

 glance at the structure of the eye in the different species of salpa is 

 enough, however, to show that such a comparative study is likely to 

 prove of considerable value within the group. 



So far as I can learn, the ciliated funnel is the only structure as yet 

 described in salpa that has been regarded as homologous with any part 

 of the sub-neural gland of ascidians. 1 In the course of the present paper 

 I shall describe certain other structures, till now undescribed (see foot- 

 note), that seem beyond question to have the closest relation to the 

 ascidian gland itself and to the lateral ducts from the gland of phallusia 

 mammillata to the peribranchial chamber. I shall try to show also that 

 a certain part of the ganglion of salpa is homologous with the sub-neural 

 gland of ascidians rather than with any part of the ascidian ganglion. 



SECTION 1. The Eyes. 



DESCRIPTIVE. 



The most noticeable feature of the anatomy of the eye of salpa and 

 cyclosalpa is its quite uniform shape throughout the solitary forms of 

 the different species, and the strongly contrasted diversity of form that it 

 shows in the chain individuals of these same species. These diverse 

 forms are constant and characteristic for each species. In no case does 

 the shape of the eye in the chain-form agree with the shape in the 

 solitary form of the same or any other species. The variations in the 

 histological structure must be described in detail. The eye of the chain 

 individual is closely related to that of the solitary salpa, for it passes 

 through an ontogenetic stage corresponding in shape to the adult condi- 

 tion of the latter. The eye of the solitary salpa must then be regarded 

 as the type from which the eye of the chain-salpa has diverged to a 



1 In a preliminary notice of this paper I gave a brief description of the organs here 

 described at greater length [12J. 



