.26 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



the group, Erytliropsls cochlea (fig. SS. 7), the diameter of the lens is only 

 16/t while the length of the body is 131/^. In Poiichetia poli/plicmus (fig. 00, 11) 

 the ratio between the length of liody and that of the lens shows the greatest 

 divergence, the former being about 104/^ and the latter 8m. In P. piirpurescens 

 also this same divergence exists, though to a less extent, the length of the body 

 being 58/^ and that of the lens about l.ot^. In most of the other species, however, 

 a closer correlation is found between the relative lengths of body and lens. 



Tlie size of the melanosome in relation to that of the lens is variable, due 

 largely, perhaps, to the amoeboid character of the pigment. In most species 

 it seems to be nearly equal to the lens in size, though probably not actually so, 

 since the lens is usually partly liuried within its substance. In a few species, 

 notably in Ne))iafo(h')iii(i)i torpedo (fig. NN, 3), the melanosome has a relatively 

 minute size. In Enjihropsis corniita (fig. RR, 1), on the other hand, the mela- 

 nosome has a size equal to several times that of the lens. 



The simplest form of the melanosome is seen in Protopsis neapolitann 

 (pi. 9, fig. 96), where its relative size is also less than that of any other species 

 except in Neiuatodiuium torpedo. Here it is a loose aggregate of black pig- 

 ment granules massed together at the anterior end of the lens, and apparently 

 lacking the central core. A still looser aggregation of pigment is found in 

 PoucJietia poucJieti (pi. 11, fig. 125), l)ut in this species the relative mass and 

 size of the discrete particles of pigment have l)ecome much greater. 



The melanosome throughout the entire group is mobile to the extent of 

 moving freely around the lens, though no evidence of its movement to another 

 part of the body has ever 1)een observed. While under observation the pigment 

 will spread over the face of the lens so that the latter is almost entirely obsciired 

 (pi. 12, fig. 130), or will recede mitil it embraces only the base of the lens (pi. 12, 

 fig. 131). In some species amoeboid movements are noticeable, long pseudo- 

 podia being thrown out, sometimes around the lens (pi. 8, fig. 87), or away from 

 the lens into the surrounding cytoplasm (pi. 11, figs. 121, 126; pi. 12, fig. 127). 

 In many individuals while mider oliservation this movement was continued so 

 that no two camera sketches, made at short intervals of time, gave the same 

 oxitlines for this remarkable organelle. 



The center of the more highly integrated melanosome is occupied by a core 

 of highly colored pigment (fig. RR, core). This is usually red, often brilliant 

 in the more highly specialized forms (pi. 12. fig. 129) and light in tone in some 

 of the others (pi. 11, figs. 118, 119). It apparently is not amoeboid, but seems 

 to be connected with the base of the lens and forms the center or core around 

 which the black pigment wraps itself. The character of its connection with 

 the lens has not been clear in our material. At the time of c^iiolysis of the 

 body the ocellus is iisually the last part of the organism to disappear. The 

 core then separates itself from both the lens and the black pigment and appears 

 as a red subspheroidal body, which gradually wastes away without iuiparting 

 its own tint to the surrounding water (figs. TT, 4-8). The black pigment also 



