240 



Mr. A. Sedgwick. On the Fertilised [Nov. 26. 



in intensity of staining. The deeply- staining bodies in the nucleus 

 are, I think, placed in the strands of the pale reticulum ; but of this 

 I am not certain. 



This nucleus then consists of a simple spongework of protoplasm, 

 differing only from the external protoplasm in the fact that the stain- 

 ing matter is aggregated into small masses and into the septum 

 already mentioned. The apparent nuclear membrane is simply part of 

 the protoplasm at the junction of the modified (nuclear) and unmodi- 

 fied (cell-substance) part of the protoplasmic network. 



2. A form closely resembling the above, except in the fact that the 

 nuclear spongework is stained slightly, though not quite so deeply as 

 some of the extra-nuclear protoplasm. There are only two small 

 deeply-staining masses, which are not so conspicuous as in the first 

 form. 



We may state the difference between these two nuclei thus : in the 

 first form the chromatin of the nucleus is aggregated into a number 

 of small masses, while in the second form the chromatin is diffused 

 throughout the nuclear reticulum. The word chromatin being used 

 to denote the property which enables the protoplasm to take up and 

 retain the staining matter. The extra-nuclear protoplasmic threads 

 possess this property, and may be said to possess chromatin, but it is 

 in a diffused form, as in the second form of nucleus. 



3. In the third form the nucleus is divided by a number of septa, 

 radiating from its centre, into chambers. The chambers are partially 

 divided up into secondary chambers by prolongations of the septa. 

 The septa are continuous externally with the extra-nuclear proto- 

 plasmic reticulum. It is impossible to speak of a distinct boundary 

 of the nucleus in this form, and the substance of the nuclear septa 

 and their prolongations is exactly similar in appearance and staining 

 properties to the strands of the surrounding protoplasmic network or 

 spongework. 



A number of chromatin masses occur in each chamber of this 

 radiate nucleus — they appear to lie in the offshoots of the septa into 

 the chambers and in delicate expansions of these. But it is impos- 

 sible to determine exactly the relation of these chromatin globules to 

 the protoplasmic network in the nucleus. 



This form of nucleus is most interesting, because were it not for 

 the chromatin masses the nucleus would be quite undistinguishable 

 from the surrounding protoplasm, except, perhaps, by the fact that 

 the meshes of the network {i.e., network as seen in section) are rather 

 larger than in the protoplasm immediately around the nncleus. 



The most important, and at the same time most certain, of these 

 observations on the nucleus of the fertilised ovum of Peripatus, is that 

 the intra-nuclear and extra-nuclear reticulum are both continuous 

 with the so-called nuclear membrane. 



